Correlations of patch test reactivity and the repeated open application test (ROAT)/provocative use test (PUT)

Skin irritation potential of cosmetic preservatives: An exposure-relevant study

BACKGROUND

Preservatives represent one of the main causes of skin irritation and contact allergies.

AIMS

To comprehensively evaluate the skin irritation potential of phenoxyethanol, methylparaben, propylparaben, imidazolidinyl urea, and DMDM hydantoin under regulatory acceptable concentrations.

METHODS

A patch test and repeated open application test (ROAT) were applied to evaluate skin irritation in vivo. In vitro alternative methods consisting of the keratinocyte cytotoxicity assay, red blood cell (RBC) test, and hen's egg test-chorioallantoic membrane (HET-CAM) were performed to elucidate the mechanism of preservative-induced irritation responses.

RESULTS

The patch test showed that all test substances showed a weak erythema response. Propylparaben had the highest occlusive irritancy potential in the patch test, owing to damage to the cell membrane. The two formaldehyde releasers showed noticeable skin irritation potential in the ROAT through their cytotoxicity to keratinocytes, while a visible response was observed after applying phenoxyethanol and the two parabens. No filtration was noticed in the in vivo tests, which might be attributed to the failure of subcutaneous vessel alteration by the preservatives.

CONCLUSIONS

Commonly used cosmetic preservatives have minor skin irritation potential with mild erythema reaction under practical use, especially formaldehyde releasers and propylparaben.

Allergy Testing

Allergic diseases are common in outpatient primary care. Allergy testing can guide management to determine allergy as a cause of symptoms and target therapeutic interventions. This article provides a review of common methods of allergy testing available so that physicians may counsel and refer patients appropriately. Immediate-type hypersensitivity skin tests can be used for airborne allergens, foods, insect stings, and penicillin. Radioallergosorbent testing can be used to evaluate immediate-type hypersensitivity. Delayed-type hypersensitivity or patch-type skin tests are used in patients with suspected contact dermatitis.

International survey on skin patch test procedures, attitudes and interpretation

BACKGROUND

Skin patch test is the gold standard method in diagnosing contact allergy. Although used for more than 100 years, the patch test procedure is performed with variability around the world. A number of factors can influence the test results, namely the quality of reagents used, the timing of the application, the patch test series (allergens/haptens) that have been used for testing, the appropriate interpretation of the skin reactions or the evaluation of the patient's benefit.

METHODS

We performed an Internet -based survey with 38 questions covering the educational background of respondents, patch test methods and interpretation. The questionnaire was distributed among all representatives of national member societies of the World Allergy Organization (WAO), and the WAO Junior Members Group.

RESULTS

One hundred sixty-nine completed surveys were received from 47 countries. The majority of participants had more than 5 years of clinical practice (61 %) and routinely carried out patch tests (70 %). Both allergists and dermatologists were responsible for carrying out the patch tests. We could observe the use of many different guidelines regardless the geographical distribution. The use of home-made preparations was indicated by 47 % of participants and 73 % of the respondents performed 2 or 3 readings. Most of the responders indicated having patients with adverse reactions, including erythroderma (12 %); however, only 30 % of members completed a consent form before conducting the patch test.

DISCUSSION

The heterogeneity of patch test practices may be influenced by the level of awareness of clinical guidelines, different training backgrounds, accessibility to various types of devices, the patch test series (allergens/haptens) used for testing, type of clinical practice (public or private practice, clinical or research-based institution), infrastructure availability, financial/commercial implications and regulations among others.

CONCLUSION

There is a lack of a worldwide homogeneity of patch test procedures, and this raises concerns about the need for standardization and harmonization of this important diagnostic procedure.

Review of allergic contact dermatitis: Scratching the surface

Contact dermatitis-including allergic contact dermatitis (ACD)-n and results in over four million lost work days per year in the United States alone. ACD is a classic example of a type IV delayed hypersensitivity reaction, and represents a significant burden on the health system, economy, and patient quality of life. Thorough history taking, clinical examination, histologic evaluation, and patch testing are keys to diagnosing contact dermatitis. Patch testing, especially with comprehensive and customized panels based on the patient’s exposure history, is particularly useful in identifying potential allergens in the case of allergic contact dermatitis. ACD management requires a combination of direct medical intervention, patient education, and appropriate environmental modification to prevent exposure to offending allergens in the home or workplace. Continuing advances in the study of ACD has led to an increased understanding of the disease processes, new methods for diagnosis, and improved management. This article reviews ACD-aiming to connect recent investigational data with the current clinical understanding of disease pathophysiology, diagnostic techniques, and management strategies.

The impact of surface loading and dosing scheme on the skin uptake of fragrances

This study compared the skin uptake of γ-undecalactone, decanol, and dodecyl acetate in an in vitro, un-occluded penetration assay in which they were applied to porcine skin at different finite loadings and application schemes. The pattern of fractional uptake differed between the chemicals and did not show the often assumed inverse correlation with surface loading. Furthermore, the mass uptake of identical cumulative amounts of the chemicals was not always additive. These results show that the uptake of fragrances in absence of occlusion and at finite loadings is chemical-specific and depends on the surface loading, the application scheme, and most probably, on the effects of the chemicals on the skin barrier efficiency. The observed lack of additivity might explain some of the differences in the responses observed in patch and repeated open application tests, and the boosting of the allergic state in sensitized individuals by sub-clinical exposures.

The relationships between exposure dose and response in induction and elicitation of contact hypersensitivity in humans

Like all physiological systems, the human immune system exhibits dose-response relationships in its reactions. The strength of sensitization is related to the potency of the immunogen and the dose that reaches the immune system. In skin, as sensitizing dose per unit area (mug cm(-2)) is increased on a log scale, there is a sigmoid dose-response curve for subsequent reactivity. Similarly, the response to elicitation shows a classical sigmoid response to increasing challenge dose, with the dose per unit area again being the determinant. There is a clear inverse correlation between the strength of sensitization and the subsequent dose of antigen to which an individual will respond. This is reflected in the different challenge systems used to diagnose the existence of allergic contact sensitization to a given allergen. The occluded patch test aims to use the highest concentration possible to detect the weakest degrees of allergy, whereas the repeated open application test uses much lower concentrations similar to those encountered in real life, applied repeatedly but without occlusion, to assess clinical relevance. Many authors have attempted to use the lowest concentrations to which rare, highly sensitized individuals can react to define the concentrations which might be free of risk in terms of inducing allergic sensitization. However, it is clear that the dose-response relationships for induction of sensitivity by repeated low-dose exposures must be carefully defined in future studies. This article reviews the dose-response relationships of human contact sensitization.

Contact dermatitis in agriculture

Dermatitis in agricultural workers, albeit a common entity, infrequently receives scrutiny as to mechanism and prevention. We briefly describe potential mechanisms, examples for each, and offer an algorithm for etiologic diagnoses.

Oat sensitization in children with atopic dermatitis: prevalence, risks and associated factors

BACKGROUND

Topical treatments of atopic dermatitis (AD) may be responsible for cutaneous allergies. Percutaneous sensitization to oat used in emollients/moisturizers has already been reported. Our objectives were to measure the prevalence of oat sensitization in AD children, to assess its relevance, and to look at related parameters.

METHODS

We recruited prospectively children with AD referred for allergy testing between June 2001 and December 2004. Atopy patch tests (APT) and skin prick tests (SPT) to oat proteins (1%, 3% and 5%) and to the European standard series were performed followed by oral food challenge (OFC) and repeated open application test (ROAT) in the oat-sensitized group.

RESULTS

About 302 children were enrolled. Oat APT and SPT were positive in 14.6% and 19.2% of cases, respectively. Children under 2 years of age were more likely to have positive APT. In oat-sensitized children, OFC and ROAT were positive in 15.6% (five of 32) and 28% (seven of 25) of cases, respectively. Thirty-two percentage of oat cream users had oat-positive atopy patch test (APT) vs 0% in the nonusers group.

CONCLUSIONS

Oat sensitization in AD children seen for allergy testing is higher than expected. It may be the result of repeated applications of cosmetics with oats on a predisposed impaired epidermal barrier. We suggest avoiding topical-containing oat proteins in infants with AD.

An evaluation of dose/unit area and time as key factors influencing the elicitation capacity of methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) in MCI/MI-allergic patients

Methylchloroisothiazolinone and methylisothiazolinone (MCI/MI) contact allergy affects 1-3% of patch-tested patients in European centres. The aim of the present study was to evaluate the importance of the factors--time and concentration (dose/per unit area)--in the elicitation capacity by means of a repeated open application test (ROAT) experimental design. The study was designed as a double-blind, placebo-controlled, dose-response ROAT preceded by a diagnostic patch testing. 25 subjects with confirmed MCI/MI allergy and 10 healthy, non-MCI/MI allergic control subjects were exposed to 0.025 microg/cm2 (2 p.p.m.) of MCI/MI/unit area of the skin for 4 weeks. After a wash-out period of at least 4 weeks, the subjects were exposed to 0.094 microg/cm2 (7.5 p.p.m.) of MCI/MI/unit area of the skin for 4 weeks. The study showed the importance of both time and exposure in the elicitation process. It demonstrated that the elicitation threshold for MCI/MI is expected to be in the proximity of 0.025 microg/cm2 although it was not possible to establish a definitive elicitation threshold for MCI/MI in this study.