Relationship between mite, cat, and dog allergens in reservoir dust and ambient air

Environmental influences on childhood asthma: Allergens

Allergen exposure is associated with the development of allergen-specific sensitization, but their relationship is influenced by other contemporaneous exposures (such as microbial exposure) and the genetic predisposition of the host. Clinical outcomes of the primary prevention studies that tested the effectiveness of allergen avoidance in pregnancy and early life on the subsequent development of sensitization and asthma published to date are inconsistent. Therefore, we cannot provide any evidence-based advice on the use of allergen avoidance for the primary prevention of these conditions. The evidence about the impact of allergen exposure among and among sensitized children with asthma is more consistent, and the combination of sensitization and high exposure to sensitizing allergen increases airway inflammation, triggers symptoms, adversely impacts upon disease control, and is associated with poorer lung function in preschool age. However, there are differing opinions about the role of inhalant allergen avoidance in asthma management, and recommendations differ in different guidelines. Evidence from more recent high-quality trials suggests that mite allergen-impermeable bed encasings reduce hospital attendance with asthma attacks and that multifaceted targeted environmental control improves asthma control in children. We therefore suggest a pragmatic approach to allergen avoidance in the management of childhood asthma for clinical practice, including the recommendations to: (1) tailor the intervention to the patient's sensitization and exposure status by using titer of allergen-specific IgE antibodies and/or the size of the skin test as indicators of potential response; (2) use a multifaceted allergen control regime to reduce exposure as much as possible; and (3) start intervention as early as possible upon diagnosis.

Animal Allergens, Endotoxin, and β-(1,3)-Glucan in Small Animal Practices: Exposure Levels at Work and in Homes of Veterinary Staff

OBJECTIVES

In veterinary settings, high exposures to animal allergens and microbial agents can be expected. However, occupational exposure levels are largely unknown. The objective of this study was to estimate the allergen, endotoxin, and β-(1,3)-glucan concentrations in small animal practices and in the homes of practice employees.

METHODS

Dust samples were collected using electrostatic dust fall collectors in diverse rooms of 36 small animal practices, as well as in employees' homes. Major animal allergens (Fel d 1, Can f 1, Ory c 3, Cav p 1, Equ c 1, Bos d 2), domestic mite (DM) allergens, and β-(1,3)-glucan levels were measured using enzyme immunoassays. Endotoxin was determined using the Limulus amoebocyte lysate assay. Influences on exposure levels were analyzed using multilevel models.

RESULTS

The levels of Can f 1, Fel d 1, Ory c 3, and Cav p 1 were up to 30 times higher in practices compared with homes without animals, but significantly lower compared with the homes with the respective pet. Although horses were not treated in the practices, Equ c 1 was found in 87.5% of samples, with the highest concentrations measured in changing rooms. DM levels were significantly lower in practices than in all private homes, and endotoxin levels were similar to those in homes with pets. In the practice itself, exposure levels were significantly influenced by animal presence, type of the room, and area per employee; whereas, room volume and diverse cleaning measures had mostly no effect.

CONCLUSIONS

Exposure to animal allergens is high in veterinary practices, but it does not reach levels of households with pets. Domestic mite allergen and endotoxin exposure seem to be low for workers in veterinary practices. The high Equ c 1 detection rate strongly indicates dispersal of allergens, most likely through clothing and hair.

The investigation of the influence of thermal plume and breathing on sleeping microenvironment

Most of humans' lifetime was spent indoor, especially in bedroom. Thus, understanding the characteristics of the sleep microenvironment is a prerequisite for better control and improvement of our sleeping environment. This study investigated the temperature and velocity field above the heads of sleeping people with supine postures, and explored the interactions between the thermal plume and the breathing airflow, where both the thermal manikins and real human subjects were used in our experiment settings. Three different breathing modes were considered in this study, where the non-breathing mode was used to investigate the characteristics of the thermal plume, and the synergy of the mouth and nose breathing mode on the thermal plume was also investigated. The results showed that the thermal plume of a supine posture person was not strong compared to that of a standing or sitting person, and the breathing airflow could influence the development of the thermal plume. Over the head of a sleeping person, the velocity of the thermal plume could be increased by both of the breathing modes, but no significant difference in the velocity and temperature field was found for the two breathing modes. It was also found that pollutants near the bed surface could be brought to the breathing zone with low velocity airflow, but could be blocked by the nasal exhalation jet. The findings in this study could provide theoretical support and guidance to improve the air quality in the breathing zone.

Dust-mite inducing asthma: what advice can be given to patients?

Introduction: Amongst allergic asthmatics, high allergen exposure increases asthma severity. However, there is no consensus on the role of mite allergen avoidance in the management of asthma, and various guidelines differ in their recommendations. Areas covered: Several systematic reviews/meta-analyses on mite avoidance in the management of asthma have been published, and their findings have been used for a call to provide a recommendation in British guidelines that dust-mite control measures should not be recommended. However, there are several problems with such analysis (such as combining studies in adults and children), and we question whether these are appropriate tools to evaluate available evidence about mite allergen avoidance, and whether it is correct to rely disproportionately on the results of meta-analyses/systematic reviews to inform clinical practice in this area. Recent evidence in children suggests that mite-impermeable bed encasings reduce emergency hospital attendance with severe asthma exacerbations. Expert opinion: The practical questions include how to achieve a sufficient real-life reduction allergen exposure, and how to identify patients who will benefit from effective intervention. The intervention should start early in the natural history of asthma, and consideration for choosing patients should include using the titre of allergen-specific IgE antibodies or the size of skin test wheal as an indicator.

Effects of indoor particulate matter exposure on daily asthma control

BACKGROUND

Household dust often contains aeroallergens, such as the house dust mite antigen Der p 1. It has been proposed that overnight exposure to particulate matter from bedding and other sources may be an important driver of atopic asthma. Whether variability in overnight particulate matter exposure is a significant determinant of asthma control is unknown.

OBJECTIVE

To test the hypothesis that overnight particulate matter exposure is associated with day-to-day symptoms, lung function, and airway inflammation in patients with asthma who are sensitized to house dust mite.

METHODS

We undertook a prospective, single-center panel study in 28 adults with asthma and house dust mite sensitization. Overnight exposure to particulate matter was measured using a commercially available indoor air quality monitor. Symptom scores, peak expiratory flow, and exhaled nitric oxide were measured and electronically recorded daily. Participants were followed up for 12 weeks and attended study visits every 4 weeks, at which they underwent spirometry and completed the Asthma Control Questionnaire and Asthma Quality of Life Questionnaire. Data were analyzed using cross-correlation and linear mixed-effects models.

RESULTS

No significant associations were observed between overnight particulate matter exposure and clinical outcomes measured daily or at study visits.

CONCLUSION

Natural variability in overnight particulate matter exposure does not appear to be a major determinant of daily asthma control in patients with asthma and house dust mite sensitization.

Sampling Devices for Indoor Allergen Exposure: Pros and Cons

PURPOSE OF REVIEW

To review current indoor allergen sampling devices, including devices to measure allergen in reservoir and airborne dust, and personal sampling devices, with attention to sampling rationale and major indoor allergen size and characteristics.

RECENT FINDINGS

While reservoir dust vacuuming samples and airborne dust volumetric air sampling remain popular techniques, recent literature describes sampling using furnace filters and ion-charging devices, both which help to eliminate the need for trained staff; however, variable correlation with reservoir dust and volumetric air sampling has been described. Personal sampling devices include intra-nasal samples and personal volumetric air samples. While these devices may offer better estimates of breathable allergens, they are worn for short periods of time and can be cumbersome. Reservoir dust sampling is inexpensive and is possible for families to perform. Airborne dust sampling can be more expensive and may better quantify cat, dog, and mouse allergen exposure. Personal sampling devices may offer a better representation of breathable air.

Endotoxin, cat, and house dust mite allergens in electrostatic cloths and bedroom dust

Environmental exposure to endotoxin, Fel d I (cat) allergen and Der p I (house dust mite) allergen have been associated with asthma symptoms and have been measured in the environment using various sampling methods, including the electrostatic dust collector. The objectives of this study were to investigate whether levels of endotoxin and allergens were detectable in electrostatic dust collectors and to examine the correlation of allergen and endotoxin levels between electrostatic dust collectors and vacuum sampling methods (floor dust and mattress dust). Electrostatic cloths, bedroom floor dust and mattress dust samples from a subset of 60 homes were randomly selected from the Health of Occupants of Mouldy Homes study for allergen and endotoxin analysis. Fel d I and Der p I allergens were analyzed by double monoclonal antibody ELISA and endotoxin by the kinetic Limulus amoebocyte lysate assay. An enhanced ELISA method was used to analyze Der p I in the electrostatic cloths. Endotoxin was detected in all samples, however Fel d I and Der p I were not detected in all electrostatic dust collector samples (detection in 53% and 15% of cloths respectively). No correlations were found between cloth and dust samples for endotoxin or Der p I, but moderate-to-strong correlations were found between all three sampling methods for Fel d I (r_s = 0.612-0.715, p < 0.001). Poor correlation was found between floor dust and mattress dust samples for Der p I (r_s = 0.256, p = 0.048). Electrostatic dust collectors may provide a way to measure airborne dust and allergen. Given the moderate-to-low correlations with vacuum dust sampling, this may present a unique measurement system which, when collected alongside traditional vacuum dust sampling, could provide additional exposure measures. Further studies are required to correlate endotoxin and allergen levels measured by electrostatic dust collector with air sampling and to explore the relationships between these bioaerosols, environmental factors and asthma.

The development of methods to measure exposure to a major rabbit allergen (Ory c 1)

Rabbits are used as laboratory animal models and are also popular domestic pets. Allergic responses to rabbit allergens have been documented in both settings, and several rabbit allergens identified. We have purified an 18 kD protein extracted from rabbit fur that was shown by N-terminal sequencing and mass spectrometry (MS) to be a lipocalin, identical to that identified as an odorant binding protein and an allergen with the formal nomenclature of Ory c 1. De novo sequencing of the MS peptide fragments gave additional primary sequence data of this protein. Polyclonal antisera were raised against the purified protein and used to develop two types of immunoassay. Ory c 1 content was measured in used rabbit bedding and household dust samples from homes keeping rabbits as pets. Atmospheric sampling was also undertaken in an animal facility undertaking rabbit experimental work. Ory c 1 levels in house dust where rabbits were kept as pets were between undetectable–41,290 ng·g⁻¹, and in used bedding between 370–26,740 ng·g⁻¹. Significantly higher house dust levels were found where rabbits spent large amounts, or all of, their time indoors. Personal air sampler levels within the animal facility were between 65–216 ng·m⁻³. Low levels (0.8–2 ng·m⁻³) were found in the facility's changing rooms, but undetected in the entrance lobby, office and laundry. We believe that these immunochemical assays may be used to identify activities in the occupational and domestic setting which produce higher levels of exposure to rabbit allergens, and where measures to control exposure may be warranted to reduce potential risk of allergic outcomes.

How clean is your house? A study of house dust mites, allergens and other contents of dust samples collected from households

Household dust contains an array of constituents, including house dust mites (HDM) and the HDM allergen, Der p 1, which can cause sensitivities such as asthma and eczema. Vacuuming can help alleviate symptoms, yet little is understood about cleaning behaviour in different households. This pilot study investigated the contents of dust from four household types (students; over 65 s; and families with and without pets). This was then related to cleaning behaviours and perceptions of cleanliness. Our investigation found that HDMs and Der p 1 were present in all households and sampling locations, including participants' cars. The median Der p 1 was greatest in the living room, though results varied. Demographic group was a determinant for the number of human and pet hairs present in dust. Surprisingly, vacuuming was the most disliked task overall. This information requires consideration when developing cleaning products and advising individuals with dust-related health issues.

Airborne protein concentration: a key metric for type 1 allergy risk assessment-in home measurement challenges and considerations

Background

Exposure to airborne proteins can be associated with the development of immediate, IgE-mediated respiratory allergies, with genetic, epigenetic and environmental factors also playing a role in determining the likelihood that sensitisation will be induced. The main objective of this study was to determine whether airborne concentrations of selected common aeroallergens could be quantified in the air of homes using easily deployable, commercially available equipment and analytical methods, at low levels relevant to risk assessment of the potential to develop respiratory allergies. Additionally, air and dust sampling were compared and the influence of factors such as different filter types on allergen quantification explored.

Methods

Low volume air sampling pumps and DUSTREAM^® dust samplers were used to sample 20 homes and allergen levels were quantified using a MARIA^® immunoassay.

Results

It proved possible to detect a range of common aeroallergens in the home with sufficient sensitivity to quantify airborne concentrations in ranges relevant to risk assessment (Limits of Detection of 0.005–0.03 ng/m³). The methodology discriminates between homes related to pet ownership and there were clear advantages to sampling air over dust which are described in this paper. Furthermore, in an adsorption–extraction study, PTFE (polytetrafluoroethylene) filters gave higher and more consistent recovery values than glass fibre (grade A) filters for the range of aeroallergens studied.

Conclusions

Very low airborne concentrations of allergenic proteins in home settings can be successfully quantified using commercially available pumps and immunoassays. Considering the greater relevance of air sampling to human exposure of the respiratory tract and its other advantages, wider use of standardised, sensitive techniques to measure low airborne protein concentrations and how they influence development of allergic sensitisation and symptoms could accelerate our understanding of human dose–response relationships and refine our knowledge of thresholds of allergic sensitisation and elicitation via the respiratory tract.

Respiratory Allergens from Furred Mammals: Environmental and Occupational Exposure

Furry mammals kept as pets, farm and laboratory animals are important allergen sources. The prevalence of sensitization to furred mammals appears to be increasing worldwide. Several mammalian allergens from diverse species are well characterized with regard to their molecular structure and immunogenicity, and some are already available for component-resolved allergy diagnostics. The distribution of various mammalian allergens has been extensively studied during the past few decades. Animal allergens were found to be ubiquitous in the human environment, even in places where no animals reside, with concentrations differing considerably between locations and geographical regions. This review presents an overview of identified mammalian respiratory allergens classified according to protein families, and compiles the results of allergen exposure assessment studies conducted in different public and occupational environments.

Respiratory Allergens from Furred Mammals: Environmental and Occupational Exposure

Furry mammals kept as pets, farm and laboratory animals are important allergen sources. The prevalence of sensitization to furred mammals appears to be increasing worldwide. Several mammalian allergens from diverse species are well characterized with regard to their molecular structure and immunogenicity, and some are already available for component-resolved allergy diagnostics. The distribution of various mammalian allergens has been extensively studied during the past few decades. Animal allergens were found to be ubiquitous in the human environment, even in places where no animals reside, with concentrations differing considerably between locations and geographical regions. This review presents an overview of identified mammalian respiratory allergens classified according to protein families, and compiles the results of allergen exposure assessment studies conducted in different public and occupational environments.

Short-term dynamics of indoor and outdoor endotoxin exposure: Case of Santiago, Chile, 2012

Indoor and outdoor endotoxin in PM2.5 was measured for the very first time in Santiago, Chile, in spring 2012. Average endotoxin concentrations were 0.099 and 0.094 [EU/m(3)] for indoor (N=44) and outdoor (N=41) samples, respectively; the indoor-outdoor correlation (log-transformed concentrations) was low: R=-0.06, 95% CI: (-0.35 to 0.24), likely owing to outdoor spatial variability. A linear regression model explained 68% of variability in outdoor endotoxins, using as predictors elemental carbon (a proxy of traffic emissions), chlorine (a tracer of marine air masses reaching the city) and relative humidity (a modulator of surface emissions of dust, vegetation and garbage debris). In this study, for the first time a potential source contribution function (PSCF) was applied to outdoor endotoxin measurements. Wind trajectory analysis identified upwind agricultural sources as contributors to the short-term, outdoor endotoxin variability. Our results confirm an association between combustion particles from traffic and outdoor endotoxin concentrations. For indoor endotoxins, a predictive model was developed but it only explained 44% of endotoxin variability; the significant predictors were tracers of indoor PM2.5 dust (Si, Ca), number of external windows and number of hours with internal doors open. Results suggest that short-term indoor endotoxin variability may be driven by household dust/garbage production and handling. This would explain the modest predictive performance of published models that use answers to household surveys as predictors. One feasible alternative is to increase the sampling period so that household features would arise as significant predictors of long-term airborne endotoxin levels.

Cat (Fel d 1) and dog (Can f 1) allergen levels in cars, dwellings and schools

Pets are an important source of indoor allergens. The aim of the study was to compare cat and dog allergen levels in cars, schools and homes. The study was carried out in 17 cars, 14 classrooms and 19 dwellings located in the highly industrialized and urbanized region of Poland. Dust and air samples were analyzed for Fel d 1 and Can f 1 using a double monoclonal ELISA assay. The highest amounts of cat and dog allergens (Fel d 1: 1169 μg/g; Can f 1: 277 μg/g) were found in dwellings with pets. Allergen concentrations were correlated with the number of animals kept at home. Although concentrations on automobile seats were lower, Fel d 1 levels exceeded 8 μg/g in 23.5 % of cars and high levels of Can f 1 (>10 μg/g) were found in 17.6 % of cars. The study revealed that cars of pet owners may be reservoirs of cat and dog allergens even when animals are not transported in them. In schools, concentrations of pet allergens did not reach high levels, but the moderate levels of Fel d 1 (≥1-8 μg/g) and Can f 1 (≥2-10 μg/g) were detected in 42.9 and 7.1 % of the investigated classrooms. Concentrations of cat and dog allergen in schools were higher than in homes without pets. While airborne Fel d 1 and Can f 1 levels were found low, residential allergen concentrations in settled dust and air were correlated. The study results suggest that classrooms and cars of pet owners may be important sites of exposure to cat and dog allergens, though the highest concentrations of Fel d 1 and Can f 1 are found in homes of pet owners.

Mites and other indoor allergens - from exposure to sensitization and treatment

House dust mites, cats and dogs are amongst the most frequent sources of indoor allergens in Europe. The fact that the allergens of house dust mites cause allergic disease through inhalation of house dust was discovered in 1964. The diagnosis of mite allergy is regularly complicated by its often nonspecific symptoms, which frequently develop insidiously and by no means always include attacks of paroxysmal sneezing and itching. Antibody-based immunological detection methods can be used to measure exposure to mite allergens. The structure and function of more than 20 allergens from Dermatophagoides pteronyssinus and D. farina are known. Other relevant indoor allergens come from mammals kept in households. Here again, allergens have been described and diagnostic as well as exposure-measurement tools are available. It is important to remember indoor pests and other „unwelcome lodgers“ as a possible cause in the case of unexplained symptoms experienced indoors. This short overview summarizes the current key points on the subject of „mites and other indoor allergens“. The present article provides an overview of several articles published in a special issue of the German journal Allergologie [February 2015; 38(2)] on the subject of „Mites and other indoor allergens“.

Effect of a novel temperature-controlled laminar airflow device on personal breathing zone aeroallergen exposure

Temperature-controlled laminar airflow improves symptoms in atopic asthmatics, but its effects on personal allergen exposure are unknown. We aimed to evaluate its effects on personal cat allergen and particulate exposures in a simulated bedroom environment. Five healthy volunteers lay under an active and an inactive temperature-controlled laminar airflow device for 175 min, in a simulated bedroom containing bedding from a cat owner. Total airborne particles (≥0.5 - ≥10 μm diameter) were quantified with a laser particle counter. Airborne allergen was sampled with Institute of Occupational Medicine filters. Inhaled exposure was sampled with nasal air samplers. Allergen-containing particles were quantified by immunoassay. Treatment reduced total airborne particles (>0.5 μm diameter) by >99% (P < 0.001) and reduced airborne allergen concentration within the breathing zone (ratio of median counts = 30, P = 0.043). Treatment reduced inhaled allergen (ratio of median counts = 7, P = 0.043). Treatment was not associated with a change in airborne allergen concentration outside of the breathing zone (P = 0.160). Temperature-controlled laminar airflow treatment of individuals in an allergen-rich experimental environment results in significant reductions in breathing zone allergenic and non-allergenic particle exposure, and in inhaled cat allergen exposure. These findings may explain the clinical benefits of temperature-controlled laminar airflow.

Measurement of aeroallergens from furnace filters

BACKGROUND

Exposure assessment is an important component of allergic disease diagnosis and management. Analysis for allergen content in vacuumed dust has been used traditionally.

OBJECTIVE

To study allergen levels of dust taken from high-efficiency furnace filters in Midwestern homes.

METHODS

Furnace filters used were FQT12 1-inch disposable filters with high-efficiency media placed in homes enrolled in the Kansas City Safe and Healthy Homes Project. Dust was removed from the filters by vacuuming. Fungal culture was used to obtain counts of viable spores. Aeroallergens Fel d1, Can f1, Mus m1, Der f1, Der p1, and Bla g2 and antigenic material from Alternaria, Aspergillus, Cladosporium, and Penicillium species were measured using commercially available immunoassay materials.

RESULTS

Sixty filters were recovered from 56 homes after an average 135 days in situ. Mean weight of dust recovered was 2.43 g and correlated well with the time the filter was in place. Viable spore counts ranged to 4.8 × 10(7) per gram of dust. Mean fungal antigenic material ranged to 42 μg per gram for Cladosporium species. Mean aeroallergen material ranged to 7 μg per gram for Fel d1. Aeroallergen measurements were above the level of detection in 100% of houses for Fel d1 and 89% of houses for Bla g2. Levels of Fel d1 and Can f1 were strongly positively correlated.

CONCLUSION

Allergens from 5 common aeroallergen species and antigenic material from 4 common fungal taxa can be measured in dust taken from high-efficiency furnace filters.

Monitoring of occupational and environmental aeroallergens-- EAACI Position Paper. Concerted action of the EAACI IG Occupational Allergy and Aerobiology & Air Pollution

Exposure to high molecular weight sensitizers of biological origin is an important risk factor for the development of asthma and rhinitis. Most of the causal allergens have been defined based on their reactivity with IgE antibodies, and in many cases, the molecular structure and function of the allergens have been established. Significant information on allergen levels that cause sensitization and allergic symptoms for several major environmental and occupational allergens has been reported. Monitoring of high molecular weight allergens and allergen carrier particles is an important part of the management of allergic respiratory diseases and requires standardized allergen assessment methods for occupational and environmental (indoor and outdoor) allergen exposure. The aim of this EAACI task force was to review the essential points for monitoring environmental and occupational allergen exposure including sampling strategies and methods, processing of dust samples, allergen analysis, and quantification. The paper includes a summary of different methods for sampling and allergen quantification, as well as their pros and cons for various exposure settings. Recommendations are being made for different exposure scenarios.

Domestic exposure to fungal allergenic particles determined by halogen immunoassay using subject's serum versus particles carrying three non-fungal allergens determined by allergen-specific HIA

Studies that estimate indoor aeroallergen exposure typically measure a pre-selected limited range of allergens. In this study, inhalable aeroallergen particles were quantified using the halogen immunoassay (HIA) to determine the contribution of fungal and non-fungal aeroallergens to total allergen exposure. Bioaerosols from 39 homes of fungal-allergic subjects were sampled using inhalable fraction samplers and immunostained by HIA using resident subject's immunoglobulin E (IgE) to detect allergen-laden particles. Fungal aerosols as well as particles carrying mite, cat, and cockroach allergens were identified and enumerated by HIA. Reservoir dust-mite (Der p 1), cat (Fel d 1), and cockroach (Bla g 1) allergen concentrations were quantified by ELISA. Fungal particles that bound subject's IgE in the HIA were 1.7 (bedroom)- and 1.4 (living room)-fold more concentrated than Der p 1, Fel d 1, and Bla g 1 allergen particles combined. Predominant fungal conidia that bound IgE were derived from common environmental genera including Cladosporium and other fungi that produce amerospores. Airborne mite, cat, and cockroach allergen particle counts were not associated with reservoir concentrations determined by ELISA. This study demonstrates that inhalable fungal aerosols are the predominant aeroallergen sources in Sydney homes and should be considered in future exposure assessments.

PRACTICAL IMPLICATIONS

Indoor allergen exposure assessment studies have primarily focused on a limited range of allergen sources in samples derived from reservoir dust samples. Using an innovative immunodiagnostic approach, this study demonstrates that fungal bioaerosols are the dominant source of aeroallergen exposure in the domestic environment, providing unique insight into domestic aeroallergen exposure.

Changes in cat specific IgE and IgG antibodies with decreased cat exposure

BACKGROUND

Current understanding of the effects of reducing exposure to cat allergens is limited. It has also become clear that there are different forms of immune response to cat allergens.

OBJECTIVE

To investigate changes in skin tests and cat specific IgG and IgE antibodies when students from a home with a cat move to a college dormitory.

METHODS

Ninety-seven college students participated in a prospective study that consisted of allergy skin prick testing and serum measurement of IgE and IgG antibodies to cat at the beginning and end of one academic year in college. A subgroup returned for follow-up at the end of 2 years.

RESULTS

Among 97 students, 33% had IgG antibodies to Fel d 1 but no evidence of sensitization, 25% had positive skin test results and/or serum IgE antibodies, and 42% had negative skin test results and no detectable serum antibodies. Among the non-cat sensitized students with IgG antibodies, the titers decreased during 8 months (P = .002). Titers of IgG4 to Fel d 1 also decreased (P < .001). Among the sensitized students, no change in IgE antibodies to cat occurred in 8 months (P = .20), whereas Fel d 1 specific IgG antibodies decreased (P < .001). Thus, ratios of IgG to IgE decreased highly significantly (P = .007). Among the students with negative skin test results who returned for follow-up (n = 56), none developed positive skin test results or serum IgE antibodies.

CONCLUSION

Under conditions of marked decrease in exposure, no participants developed new-onset sensitization. Among the individuals sensitized at study entry, there were major decreases in the ratio of IgG to IgE.

Animal allergens and their presence in the environment

Exposure to animal allergens is a major risk factor for sensitization and allergic diseases. Besides mites and cockroaches, the most important animal allergens are derived from mammals. Cat and dog allergies affect the general population; whereas, allergies to rodents or cattle is an occupational problem. Exposure to animal allergens is not limited to direct contact to animals. Based on their aerodynamic properties, mammalian allergens easily become airborne, attach to clothing and hair, and can be spread from one environment to another. For example, the major cat allergen Fel d 1 was frequently found in homes without pets and in public buildings, including schools, day-care centers, and hospitals. Allergen concentrations in a particular environment showed high variability depending on numerous factors. Assessment of allergen exposure levels is a stepwise process that involves dust collection, allergen quantification, and data analysis. Whereas a number of different dust sampling strategies are used, ELISA assays have prevailed in the last years as the standard technique for quantification of allergen concentrations. This review focuses on allergens arising from domestic, farm, and laboratory animals and describes the ubiquity of mammalian allergens in the human environment. It includes an overview of exposure assessment studies carried out in different indoor settings (homes, schools, workplaces) using numerous sampling and analytical methods and summarizes significant factors influencing exposure levels. However, methodological differences among studies have contributed to the variability of the findings and make comparisons between studies difficult. Therefore, a general standardization of methods is needed and recommended.

Reducing patients' exposures to asthma and allergy triggers in their homes: an evaluation of effectiveness of grades of forced air ventilation filters

Objective

Many interventions to reduce allergen levels in the home are recommended to asthma and allergy patients. One that is readily available and can be highly effective is the use of high performing filters in forced air ventilation systems.

Methods

We conducted a modeling analysis of the effectiveness of filter-based interventions in the home to reduce airborne asthma and allergy triggers. This work used “each pass removal efficiency” applied to health-relevant size fractions of particles to assess filter performance. We assessed effectiveness for key allergy and asthma triggers based on applicable particle sizes for cat allergen, indoor and outdoor sources of particles <2.5 µm in diameter (PM_2.5), and airborne influenza and rhinovirus.

Results

Our analysis finds that higher performing filters can have significant impacts on indoor particle pollutant levels. Filters with removal efficiencies of >70% for cat dander particles, fine particulate matter (PM_2.5) and respiratory virus can lower concentrations of those asthma triggers and allergens in indoor air of the home by >50%. Very high removal efficiency filters, such as those rated a 16 on the nationally recognized Minimum Efficiency Removal Value (MERV) rating system, tend to be only marginally more effective than MERV12 or 13 rated filters.

Conclusions

The results of this analysis indicate that use of a MERV12 or higher performing air filter in home ventilation systems can effectively reduce indoor levels of these common asthma and allergy triggers. These reductions in airborne allergens in turn may help reduce allergy and asthma symptoms, especially if employed in conjunction with other environmental management measures recommended for allergy and asthma patients.

Animal allergens and their presence in the environment

Exposure to animal allergens is a major risk factor for sensitization and allergic diseases. Besides mites and cockroaches, the most important animal allergens are derived from mammals. Cat and dog allergies affect the general population; whereas, allergies to rodents or cattle is an occupational problem. Exposure to animal allergens is not limited to direct contact to animals. Based on their aerodynamic properties, mammalian allergens easily become airborne, attach to clothing and hair, and can be spread from one environment to another. For example, the major cat allergen Fel d 1 was frequently found in homes without pets and in public buildings, including schools, day-care centers, and hospitals. Allergen concentrations in a particular environment showed high variability depending on numerous factors. Assessment of allergen exposure levels is a stepwise process that involves dust collection, allergen quantification, and data analysis. Whereas a number of different dust sampling strategies are used, ELISA assays have prevailed in the last years as the standard technique for quantification of allergen concentrations. This review focuses on allergens arising from domestic, farm, and laboratory animals and describes the ubiquity of mammalian allergens in the human environment. It includes an overview of exposure assessment studies carried out in different indoor settings (homes, schools, workplaces) using numerous sampling and analytical methods and summarizes significant factors influencing exposure levels. However, methodological differences among studies have contributed to the variability of the findings and make comparisons between studies difficult. Therefore, a general standardization of methods is needed and recommended.

Cat and dog sensitization in pet shop workers

BACKGROUND

Sensitivity and symptoms related to animal proteins have been investigated in various occupational groups. However, data from pet shops are limited.

AIMS

To investigate rates of sensitivity to cats and dogs among pet shop workers, to assess the relationship between sensitivity, allergen levels and symptoms and to investigate whether passive transport from pet shops to homes is possible.

METHODS

Pet shop workers underwent interviews with a questionnaire adapted from the European Community Respiratory Health Survey. Dust samples for allergen detection were collected from pet shops using a vacuum cleaner. Skin tests were performed with common allergens. Dust samples were also obtained from the houses of 7 workers and 12 control subjects.

RESULTS

Fifty-one workers from 20 pet shops were included in the study. Thirteen (25%) workers reported work-related symptoms. Four workers had sensitivity to animal allergens. The mean cat/dog allergen levels from pet shops were 15.7 and 3.2 µg/g, respectively. There was no significant relationship between cat/dog allergen levels and work-related symptoms and sensitivity to pets. None of the dust samples collected from the homes of pet shop workers contained cat allergens. Dog allergen was detected in only one house (0.58 µg/g). Neither cat nor dog allergens were found in the homes of the 12 control subjects.

CONCLUSIONS

Although a quarter of pet shop workers reported work-related symptoms, sensitivity to cat and dog was low. These findings suggest that work-related symptoms may be due to other factors than cat and dog sensitivity.

Airborne allergens, endotoxins, and particulate matter in elementary schools, results from Germany (LUPE 2)

Allergic disorders are the most common childhood-related chronic diseases in developed countries. It is essential to assess the exposure, especially in schools, where children spend a large portion of their time. We aimed to investigate allergen and endotoxin levels in the air of schools and to observe seasonal variations of these factors. We evaluated airborne concentrations of house dust mites allergens (Der p 1, Der f 1), cat allergen (Fel d 1), and endotoxin in PM10 in 14 classrooms during the school days in the region of Munich, each over 20 consecutive days and in 1 classroom over the course of a year (at 83 days); we also tested outdoor air close to the schools. Endotoxin levels were quantified using two different analytical methods. In addition, indoor air climate parameters were measured. The median daily indoor CO2 and PM10 concentrations in the classrooms ranged from 423 to 3,135 ppm (median: 1,211 ppm) and 9 to 390 μg/m(3) (median: 127 μg/m(3)), respectively. Fel d 1 in the PM10 samples was the most frequently detected allergen, with levels from 0.02 to 1.15 ng/m(3) in a total of 301 samples (median: 0.19 ng/m(3), 95th percentile: 0.57 ng/m(3)). Der p 1 and Der f 1 were detected in only 51% and 19% of the samples, with 95th percentiles at 0.5 and 0.3 ng/m(3). Endotoxin levels in the PM10 and inhalable dust samples ranged from 0.5 to 84.1 EU/m(3) (median: 15.3 EU/m(3); 95th percentile: 58.2 EU/m(3)) and from 0.03 to 115 EU/m(3) (median: 8.4 EU/m(3); 95th percentile: 27.9 EU/m(3)). Fel d 1 and endotoxin were found in higher levels in the winter months. The results of the two different indoor sampling techniques for endotoxin were statistically significantly correlated. The results of airborne allergens indicate a generally low exposure level in classrooms. With regard to endotoxin, our study showed higher levels in schools compared with residences.

Control of airborne and liquid-borne fungal and pet allergens using microwave irradiation

In this study, the dog, cat allergens (Can f 1 and Fel d 1) and fungal allergens (Alt a 1 and Asp f 1) were aerosolized and exposed to the microwave irradiation (2450 MHz) at different output powers for up to 2 min. The allergen bioaerosols were collected by a BioSampler, and analyzed using enzyme-linked immunosorbent assay (ELISA). Control and microwave-irradiated Asp f 1 allergens were also tested with IgEs in human blood sera samples. For airborne Asp f 1 and Alt a 1 allergens, the allergenicity was shown to decrease about 50% when exposed to microwave irradiation at 385 and 119 W and relatively no change at 700 W. For airborne Can f 1 allergen, the allergenicity was shown to increase about 70% when exposed to the irradiation at 385 W, but remained relatively unchanged at 700 and 119 W. In contrast, airborne Fel d 1 allergen was observed to lose allergenicity completely at 700 W, and retained about 40% and 80% at 385 and 119 W, respectively. Radioallergosorbent (RAST) tests showed that changes detected in IgE levels in human blood sera mixtures were not statistically significant for the control and microwave-irradiated waterborne Asp f 1 allergens. This study implies that although certain allergenicity reductions were observed for some allergens in certain cases, particular care should be taken when the microwave irradiation is used to disinfect food, water, and air because of its complex effects.

Domestic mite antigens in floor and airborne dust at workplaces in comparison to living areas: a new immunoassay to assess personal airborne allergen exposure

Objectives

Allergens produced by domestic mites (DM) are among the most common allergic sensitizers and risk factors for asthma. To compare exposure levels between workplaces and living areas a new assay able to measure airborne DM antigen concentrations was developed.

Methods

At workplaces and in living areas, 213 floor dust samples and 92 personal inhalable dust samples were collected. For sensitive quantification of DM antigens, a new enzyme immunoassay (EIA) based on polyclonal antibodies to Dermatophagoides farinae extract was developed. Reactivity of five house dust mite and four storage mite species was tested. All dust samples were tested with the new EIA and with the Der f 1 and Der p 1-EIAs (Indoor Biotechnologies, UK) which detect major allergens from D. farinae and D. pteronyssinus by monoclonal antibodies. Samples below the detection limit in the DM-EIA were retested in an assay variant with a fluorogenic substrate (DM-FEIA).

Results

The newly developed DM-EIA detects antigens from all nine tested domestic mite species. It has a lower detection limit of 200 pg/ml of D.farinae protein, compared to 50 pg/ml for the DM-FEIA. DM antigens were detected by DM-EIA/FEIA in all floor dust and 80 (87%) of airborne samples. Der f 1 was found in 133 (62%) floor dust and in only 6 airborne samples, Der p 1 was found in 70 (33%) of floor samples and in one airborne sample. Der f 1 and DM concentrations were highly correlated. DM-antigens were significantly higher in inhalable airborne samples from textile recycling, bed feather filling, feed production, grain storage and cattle stables in comparison to living areas.

Conclusions

A new sensitive EIA directed at DM antigens was developed. DM antigen quantities were well correlated to Der f 1 values and were measurable in the majority (87%) of airborne dust samples. Some workplaces had significantly higher DM antigen concentrations than living areas.

Arthropod allergens in urban homes

Dust mites, cockroaches, and pets (cats, dogs) are common in homes worldwide, and many species are the source of potent allergens which cause allergic diseases. These diseases are influenced by genetic predisposition and environmental exposure. Generally, the levels of house dust mite (Der p 1 and Der f 1) and cockroach (Bla g 1, Bla g 2) allergens are used as markers of indoor exposure to arthropods.This article reviews the findings of allergens Der p 1, Der f 1, and Bla g 1 in randomly selected urban households in Zagreb (Croatia) measured from 2006 to 2010 and compares them with exposure to arthropod allergens in other countries. In short, house dust mite allergen levels in Croatian homes are low, but exposure is common; Der p 1 was found in 73 % and Der f 1 in 83 % of the households. By contrast, exposure to cockroach allergen Bla g 1 was both low and uncommon (13 %). Exposure to multiple allergens associated with sensitisation and asthma was not frequent in urban homes in Croatia. However, further studies should include monitoring of both arthropod and pet allergens in high-risk populations in inland and coastal Croatia. They should also investigate a complex dose-response relationship between exposure and sensitisation/asthma development, especially in early childhood.

Dust mite species in the households of mite-sensitive dogs with atopic dermatitis

BACKGROUND

The presence of important house dust and storage mite species in the microenvironment of atopic dogs has not been thoroughly investigated.

OBJECTIVES

To compare the presence and population of five dust mite species (Dermatophagoides farinae, Dermatophagoides pteronyssinus, Acarus siro, Tyrophagus putrescentiae and Lepidoglyphus destructor) among households with mite-sensitive atopic dogs (Group A), households with clinically healthy dogs (Group B) and households without pets (Group C, n=25) in Greece.

ANIMALS

Twenty mite-sensitive atopic dogs and 20 clinically healthy dogs.

METHODS

Dust samples were collected with a vacuum cleaner from owners' mattresses (all groups) and from dogs' sleeping areas (Groups A and B) or living room couch (Group C), once every season of the year. Following dust flotation, mites were counted and identified.

RESULTS

Dermatophagoides farinae was the most prevalent (60, 40 and 64% in Groups A, B and C, respectively), followed by D. pteronyssinus (45, 35 and 48%, respectively), whereas the three storage mites were found in fewer households. No major differences could be found between Groups A and B or between households with (Groups A and B) and without dogs (Group C) regarding the presence or numbers of the five dust mite species.

CONCLUSIONS AND CLINICAL IMPORTANCE

The presence and population of five common house dust and storage mite species does not differ among Greek households with mite-sensitive atopic dogs, households with healthy dogs and households without pets.

Molecular diagnosis in allergy

Development and progress made in the field of recombinant allergens have allowed for the development of a new concept in allergy diagnosis, molecular diagnosis (MD), which makes it possible to identify potential disease-eliciting molecules. Microarray-based testing performed with a small amount of serum sample enables clinicians to determine specific-IgE antibodies against multiple recombinants or purified natural allergen components. Performance characteristics of allergens so far tested are comparable with current diagnostic tests, but have to be confirmed in larger studies. The use of allergen components and the successful interpretation of test results in the clinic require some degree of knowledge about the basis of allergen components and their clinical implications. Allergen components can be classified by protein families based on their function and structure. This review provides a brief overview of basic information on allergen components, recombinants or purified, currently available or soon to become commercially available in ImmunoCAP or ISAC systems, including names, protein family and function. Special consideration is given to primary or species-specific sensitization and possible cross-reactivity, because one of the most important clinical utility of MD is its ability to reveal whether the sensitization is genuine in nature (primary, species-specific) or if it is due to cross-reactivity to proteins with similar protein structures, which may help to evaluate the risk of reaction on exposure to different allergen sources. MD can be a support tool for choosing the right treatment for the right patient with the right timing. Such information will eventually give clinicians the possibility to individualize the actions taken, including an advice on targeted allergen exposure reduction, selection of suitable allergens for specific immunotherapy, or the need to perform food challenges. Nevertheless, all in vitro tests should be evaluated together with the clinical history, because allergen sensitization does not necessarily imply clinical responsiveness.

Resuspension of indoor aeroallergens and relationship to lung inflammation in asthmatic children

Studies have shown links between the concentration of allergens found in homes and asthma. Inhalation of allergens present in settled residential dust can occur when the dust is resuspended via human activity or air currents. Although previous studies have measured allergen concentrations in homes, the focus has been on the presence of the allergens in settled dust samples. However, the actual inhalation exposure is to airborne allergens. The relationship between the settled dust composition and suspended allergens and endotoxin and the effect of exposure of these aeroallergens to asthmatics are not well understood for species typically present indoors. In this study, settled dust and airborne particulate matter samples were collected in the homes and school classrooms of asthmatic children of ages 9 to 16 and analyzed for endotoxin and allergens including dust mite and cockroach allergen, and dog and cat dander (Der p1, Der f1, Bla g1, Can f1, and Fel d1, respectively). Concentrations of cockroach allergen were below detection limit for all samples. Measurements of the settled dust samples show higher dust mite allergen in bedroom samples than in living room samples. Concentrations of airborne endotoxin and indoor allergens were generally higher in the homes than those measured at school. Within the homes, higher concentrations of airborne allergens and endotoxin were observed in the living rooms compared to the bedrooms. Resuspension rates for endotoxin, dust mite allergen, and, cat and dog dander were estimated in this study. Calculated resuspension rates for cat dander (8.1x10(-7)+/-3.5x10(-7)min(-1)) and dust mite allergen (2.1x10(-6)+/-7.6x10(-7)min(-1)and 1.4x10(-5)+/-4.6x10(-6)min(-1) for Der p 1 and Der f 1, respectively) were found to be higher than those for dog dander (3.1x10(-7)+/-1.3x10(-7)min(-1)) and endotoxin (3.6x10(-7)+/-1.6x10(-7)min(-1)). Markers of asthma inflammation including nitrate in exhaled breath condensate (EBC) and exhaled nitric oxide (eNO), were correlated with the concentrations of dust mite allergen (Der p 1) (Spearman r=0.598; p-value=0.068 for EBC and Spearman r=0.819; p-value=0.007 for eNO) and cat dander (Fel d 1) (Spearman r=0.917; p-value=0.0002 for EBC and Spearman r=0.697; p-value=0.054 for eNO) present in PM(10) samples.

Control of asthma triggers in indoor air with air cleaners: a modeling analysis

BACKGROUND

Reducing exposure to environmental agents indoors shown to increase asthma symptoms or lead to asthma exacerbations is an important component of a strategy to manage asthma for individuals. Numerous investigations have demonstrated that portable air cleaning devices can reduce concentrations of asthma triggers in indoor air; however, their benefits for breathing problems have not always been reproducible. The potential exposure benefits of whole house high efficiency in-duct air cleaners for sensitive subpopulations have yet to be evaluated.

METHODS

We used an indoor air quality modeling system (CONTAM) developed by NIST to examine peak and time-integrated concentrations of common asthma triggers present in indoor air over a year as a function of natural ventilation, portable air cleaners, and forced air ventilation equipped with conventional and high efficiency filtration systems. Emission rates for asthma triggers were based on experimental studies published in the scientific literature.

RESULTS

Forced air systems with high efficiency filtration were found to provide the best control of asthma triggers: 30-55% lower cat allergen levels, 90-99% lower risk of respiratory infection through the inhalation route of exposure, 90-98% lower environmental tobacco smoke (ETS) levels, and 50-75% lower fungal spore levels than the other ventilation/filtration systems considered. These results indicate that the use of high efficiency in-duct air cleaners provide an effective means of controlling allergen levels not only in a single room, like a portable air cleaner, but the whole house.

CONCLUSION

These findings are useful for evaluating potential benefits of high efficiency in-duct filtration systems for controlling exposure to asthma triggers indoors and for the design of trials of environmental interventions intended to evaluate their utility in practice.

Evaluation of a low-cost electrostatic dust fall collector for indoor air endotoxin exposure assessment

Exposure to endotoxin in home environments has become a key issue in asthma and allergy research. Most studies have analyzed floor or mattress dust endotoxin, but its validity as a proxy for airborne exposure is unknown, while active airborne dust sampling is not feasible in large-scale population studies because of logistic and financial limitations. We therefore developed and evaluated a simple passive airborne dust collection method for airborne endotoxin exposure assessment. We explored an electrostatic dust fall collector (EDC), consisting of a 42- by 29.6-cm-sized folder with four electrostatic cloths exposed to the air. The EDC was tested during two 14-day periods in seven nonfarm and nine farm homes and in farm stables. In parallel, active airborne dust sampling was performed with Harvard impactors and floor dust collected by vacuuming, using nylon sampling socks. The endotoxin levels could be measured in all EDC cloth extracts. The levels (in EU/m(2)) between EDCs used simultaneously or in different sampling periods in the same home correlated strongly (r > 0.8). EDC endotoxin also correlated moderately to strongly (r = 0.6 to 0.8) with the endotoxin measured by active airborne dust sampling and living room floor dust sampling and-in farm homes-with the endotoxin captured by the EDC in stables. In contrast, endotoxin levels measured by floor dust sampling showed only a poor correlation with the levels measured by active airborne dust sampling. We therefore conclude that measuring endotoxin levels with the EDC is a valid measure of average airborne endotoxin exposure, while reproducibility over time is at least equivalent to that of reservoir dust analyses.

Sublingual immunotherapy with a standardized cat dander extract: evaluation of efficacy in a double blind placebo controlled study

BACKGROUND

Little information is available on the clinical efficacy of sublingual immunotherapy (SLIT) using extracts derived from mammalian epithelia.

OBJECTIVES

To assess clinical efficacy of cat SLIT based on natural exposure challenge test (NCT).

MATERIAL AND METHODS

Fifty cat allergic patients with rhinoconjunctivitis with or without asthma were included in a randomized double blind placebo controlled clinical trial of cat SLIT during 1 year. Twenty-five patients received active treatment and 25 placebo. Sublingual immunotherapy efficacy was assessed by natural exposure challenge to a cat in a cat-room and by skin tests. Airborne Fel d 1 levels, symptom scores and peak expiratory flow (PEF) values were monitored.

RESULTS

Thirty-three (66%) out of 50 patients completed the treatment. Fel d 1 content of the maximum concentration was 0.51 microg per ml. During the build up phase, the accumulated dose was 1.7 mug of Fel d 1 and during the entire length of the study was 17.1. No adverse reports were reported. The active group showed a marked reduction (62%) in symptoms during the NCT (P < 0.001) with no changes in placebo group. Active group also showed a reduced PEF response to cat exposure (P < 0.05), and an improvement in skin test reactivity to a standardized cat extract (P < 0.05), without significant changes in placebo group. Mean Fel d 1 exposure during the NCT was 6.2 +/- 2.21 ng/m(3).

CONCLUSIONS

The results suggest that the cat SLIT used in this study was able to improve cat allergy based on natural exposure challenge.

Spatial variability of particulates in homes: implications for infant exposure

Personal monitoring of particulate matter (PM) exposure in infants is difficult. Indirect, microenvironment modelling methods are more practical. Infants spend most of their time indoors at home and the aim of this study was to investigate spatial variations in PM concentrations within homes. Three size fractions of PM - particles with an aerodynamic diameter of less than 10 microm (PM(10)), less than 2.5 microm (PM(2.5)) and total suspended particulates (TSP) - were monitored in the homes of 77 infants (0-2 years) using a multi-stage virtual impactor. In all homes PM was monitored simultaneously in the main living room at heights of 1.4 m and 0.2 m from the floor. In 26 of these homes monitoring was also conducted simultaneously in the infant's bedroom. Further, PM(10) was measured simultaneously in the living room, bedroom and child's cot in 14 homes using a real-time photometer. All homes in the study were non-smoking households. On average, there were no significant differences between concentrations of any of the different PM size fractions measured at the two heights (living room) and between living room and bedroom concentrations. However, there were only moderate correlations in concentrations between the different microenvironments and in some homes there was considerable variation between sampling sites. From the real-time measurements there seemed to be good agreement between concentrations measured in different rooms and in the cot and short-term peak concentrations at one sampling site were often mirrored at other sites. These results suggest that, although large variations in PM concentrations between rooms within homes can occur, a single monitoring station can provide a reasonable estimate of indoor concentrations.

Childhood cat allergen exposure in three European countries: The AIRALLERG study

INTRODUCTION

Cat allergen is a major cause of morbidity among sensitised asthma patients, but little is known about distribution of cat allergen exposure and its determinants in homes.

METHODS

We measured cat allergen and potential determinants of cat allergen levels in more than 1000 homes. House dust was collected from children's mattresses and living room floors in approximately 360 homes in The Netherlands, Sweden and Germany and analysed for Fel d 1 in one central laboratory. Exposure was expressed both in concentration (ng/g) and in loads (ng/m2).

RESULTS

Levels on mattresses were similar in Sweden and Germany but higher on Dutch mattresses. Dutch floors had higher concentrations than Swedish floors, which had higher concentrations than German floors. The differences in load were less clear. Cat allergen on mattress and floor were moderately to highly correlated. The most important variable quantifying cat allergen variation was the presence of a cat. Floor cover type and last time that floor was vacuumed were important in all three countries. The ratio of cat allergen loads between mattresses from homes with and without cats was higher for Sweden and Germany than for The Netherlands. This is likely related to higher prevalence of cat ownership in The Netherlands which leads to more contamination of homes in which cats were never held. Dust samples from 27-35% of mattresses from homes without cats contained more than 1000 ng/g cat allergen.

CONCLUSION

With the exception of cat ownership and floor cover, questionnaire data on housing characteristics did not accurately predict cat allergen in the home.

New insights in allergen avoidance measures for mite and pet sensitized patients. A critical appraisal

It is widely acknowledged that avoidance of allergens such as those derived from foods, drugs, latex and stinging insects results in a complete disappearance of symptoms. By contrast, although it has been clearly shown that allergens are an important risk factor for the development of respiratory symptoms and that several avoidance measures reduce allergen levels, whether this gives clinical improvement in symptoms is debatable. Many reasons could be invoked to justify this evident discrepancy. Apart from the intrinsic methodological aspects (e.g. single or combined interventions measure, population studied, severity of respiratory symptoms, outcomes, evaluated parameters, etc.), it is important to outline that a successful approach requires that the avoided allergen is the only and real factor responsible for symptoms, the patient's education and the use of a comprehensive protocol to reduce allergen exposure. Other important factors include the involvement of the patient, the relevance of other allergens/non-specific agents, and exposure to sensitizing agents also outside patient's home. It is likely that the clinical phase of allergic airway disease and the degree of bronchial (and also nasal) remodelling, in each individual, represent relevant factors for the clinical outcome of allergen avoidance procedures. Since the management of respiratory allergy is a complex strategy (including drugs, allergen avoidance, immunological and educational interventions), it is difficult in real life to distinguish the efficacy of a single intervention in comparison to the others. A combined strategy is likely to produce better clinical results.

High-efficiency vacuum cleaners increase personal mite allergen exposure, but only slightly

BACKGROUND

High-efficiency particulate-arrest-filter vacuum cleaners are recommended to allergy sufferers although their use increases personal cat allergen exposure. We aimed to measure personal mite allergen exposure during vacuum cleaning by nasal air sampling and to compare exposures while vacuuming and emptying the vacuum cleaner bag.

METHODS

Five brand new high-efficiency vacuum cleaners were selected. An old, previously used vacuum cleaner with its original microfilter in situ was used as a control. Nasal air samples were taken prior to and during vacuum cleaning in 10 homes. Samples were processed by HALOgen assay. Personal mite and cat allergen exposure was measured as the dust compartments were emptied.

RESULTS

There was an increase in personal mite allergen exposure with vacuum cleaning, which approached significance (P = 0.058). There was no difference between the high-efficiency vacuum cleaners and the control vacuum cleaner (P = 0.141). When the dust compartments were emptied, personal mite and cat allergen exposure increased (P < 0.02). CONCLUSIONS. The increase in personal mite allergen exposure while vacuum cleaning in an area with mild to moderate mite allergen exposure is small. High-efficiency vacuum cleaners confer no benefit and cannot currently be recommended to allergy sufferers as a means of reducing personal mite allergen exposure.

High-dose allergen exposure leads to tolerance

Reports of decreased sensitization to cat allergen (Fel d 1) among individuals living with a cat or subjects exposed to high-dose cat allergen may be explained by the development of a form of high-dose tolerance resulting from natural exposure to an inhalant allergen. Although the epidemiological data regarding the relationship between exposure and sensitization to Fel d 1 are conflicting, the ability for high-dose Fel d 1 to induce a characteristic nonallergic immune response with a distinctive serum antibody profile has been established. Definition of this modified T-helper (Th)2 response to cat allergen, coupled with the renewed interest in regulatory T cells within the immunology field, has provided an avenue for exploring the mechanism by which IgE antibody-mediated responses are controlled. There is mounting evidence to suggest that the modified Th2 response is a variation of the allergic response and that the modified Th2-allergic axis is influenced by allergen dose and genetics. This article discusses putative immune mechanisms of tolerance within the context of an allergen-specific system. The relevance of high-dose allergen exposure and alternate factors such as endotoxin to the development of tolerance is considered. Fel d 1 exhibits unique molecular and immunological characteristics that may contribute to its tolerogenic properties. Major T-cell epitopes of Fel d 1 that preferentially induce regulatory factors have been defined. Furthermore, high-titer IgE antibody responses associated with atopic dermatitis are characterized by a defect in the T-cell repertoire that is specific to these epitopes. Identification of Fel d 1 epitopes that induce interleukin-10 may provide new targets for treatment.

Allergens and endotoxin in settled dust from day-care centers and schools in Oslo, Norway

Allergy to indoor allergens can cause frequent and severe health problems in children. Because little is known about the content of allergens in the indoor environments in Norway, we wanted to assess the levels of cat, dog and mite allergens in schools and day-care centers in Oslo. Allergen levels in dust samples from 155 classrooms and 81 day-care units were measured using commercially available enzyme-linked immunosorbent assay (ELISA) kits. Additionally, we measured the levels of endotoxin in 31 day-care units, using the limulus amebocyte lysate test. Most of the dust samples contained detectable amounts of cat and dog allergens. In mattress and floor dust (day-care centers), and curtain and floor dust (schools) the median Fel d 1 levels were 0.17, 0.002, 0.02 and 0.079 microg/m2, while the median Can f 1 levels were 1.7, 0.03, 0.1 and 0.69 microg/m2, respectively. Levels of cat and dog allergens in school floor dust were associated with the number of pupils with animals at home. In contrast, <1% of the samples had measurable levels of the mite allergen Der p 1. Moreover, the levels of endotoxin tended to be higher in dust from floors (1.4 ng/m2) compared with that from mattresses (0.9 ng/m2).

PRACTICAL IMPLICATIONS

To reduce allergen exposure, allergic individuals should be placed in the classes/rooms with the fewest pet owners. Moreover, mattresses in day-care centers are major reservoirs of cat and dog allergens and should be cleaned frequently.

Concentrations of cat and dust-mite allergens in dust samples from 92 large US office buildings from the BASE Study

The concentrations of cat (Fel d1) and dust-mite (Der f1 and Der p1) allergens were measured in 92 large office buildings in the US Environmental Protection Agency's Building Assessment Survey and Evaluation (BASE) Study (251 dust samples; one to four samples per building). Fel d1 was detected in almost all buildings and samples (91 buildings, 99%; 235 samples, 94%; range: <0.01-19 microg/g; median: 0.3 microg/g). Cat allergen exceeded 1 microg/g (a lower symptom threshold) in 56 samples (22%) from 45 buildings, but exceeded 8 microg/g (a sensitization threshold) in only two samples (1%) from two buildings. Der f1 or Der p1 was found in approximately half of all buildings and samples (63 and 70% of buildings; 45 and 51% of samples; range: <0.01-53 microg/g and <0.01-25 microg/g; median: <0.02 and 0.03 microg/g, respectively). Mite allergen exceeded 2 microg/g (a sensitization threshold) in seven samples (3%) from five buildings and exceeded 10 microg/g (a symptom threshold) in three samples (1%) from three buildings. Fel d1 concentration was significantly higher in samples collected in summer (June to September, 48 buildings), but cat allergen was not correlated with either mite allergen. Der f1, but not Der p1, concentration tended to be higher in samples collected in winter (December to April, 44 buildings), and the two mite allergens were significantly correlated only in winter. Cat and mite allergens were detected in 78% of representative US office buildings, but the concentrations seldom exceeded levels associated with sensitization or symptom provocation.

PRACTICAL IMPLICATIONS

The information on the concentrations of cat and dust-mite allergens in representative large US offices has expanded the baseline data available for interpretation of measurements from other building investigations. With suggested refinements, the BASE protocol for measurement of allergen concentrations in dust samples may serve as a guide to future studies of building characteristics, bioaerosol concentrations, and occupant perceptions of the indoor environment.