Contact reactions to fragrances

Odorant-responsive biological receptors and electronic noses for volatile organic compounds with aldehyde for human health and diseases: A perspective review

Volatile organic compounds (VOCs) are gaseous chemicals found in ambient air and exhaled breath. In particular, highly reactive aldehydes are frequently found in polluted air and have been linked to various diseases. Thus, extensive studies have been carried out to elucidate disease-specific aldehydes released from the body to develop potential biomarkers for diagnostic purposes. Mammals possess innate sensory systems, such as receptors and ion channels, to detect these VOCs and maintain physiological homeostasis. Recently, electronic biosensors such as the electronic nose have been developed for disease diagnosis. This review aims to present an overview of natural sensory receptors that can detect reactive aldehydes, as well as electronic noses that have the potential to diagnose certain diseases. In this regard, this review focuses on eight aldehydes that are well-defined as biomarkers in human health and disease. It offers insights into the biological aspects and technological advances in detecting aldehyde-containing VOCs. Therefore, this review will aid in understanding the role of aldehyde-containing VOCs in human health and disease and the technological advances for improved diagnosis.

The immediate patch test reaction to fragrance in patients with allergic contact dermatitis to fragrance: A prospective study

BACKGROUND

Fragrance is one of the common causes of immediate contact reaction. Knowing the prevalence of a reaction in a given population enables prioritization of allergy screening.

OBJECTIVE

The purpose of this study was to determine the prevalence of an immediate patch test reaction to fragrance in patients with fragrance allergic contact dermatitis.

METHODS

This prospective study enrolled 291 patients who were given standard patch tests for allergic contact dermatitis. Those with positive reactions were then asked to undergo additional patch tests to assess both immediate and delayed reactions to 28 different fragrance substances.

RESULTS

Cinnamic aldehyde and cinnamic alcohol were the most frequently encountered substances in positive immediate reactions and standard (delayed) patch test reactions. Immediate patch reactions to benzyl alcohol, sorbic acid, and coumarin were more frequently observed than standard patch test reactions.

LIMITATIONS

Because of the small sample size of patients who agreed to continue further patch testing evaluation, a statistical association between patient characteristics and fragrance-positive patch test reactions was difficult to establish.

CONCLUSIONS

In this population, cinnamic aldehyde and cinnamic alcohol were the most common fragrance allergens causing both immediate and delayed reactions, whereas reactions to benzyl alcohol, sorbic acid, and coumarin were frequently observed in immediate patch tests.

Insights into the Photodegradation of the Contact Allergen Fragrance Cinnamyl Alcohol: Kinetics, Mechanism, and Toxicity

Fragrances can cause general health issues, and special concerns exist surrounding the issue of skin safety. Cinnamyl alcohol (CAL) is a frequent fragrance contact allergen that has various toxic effects on indiscriminate animals. In the present study, the photodegradation transformation mechanism of CAL and toxicity evolution during this process were examined. The results showed that CAL (50 μM) can be completely degraded after 90-min ultraviolet (UV) irradiation with a degradation rate of 0.086 min^-1 . Increased toxicity on bioluminescent bacteria was observed during this process, with lethality increasing from 10.6% (0 min) to 50.2% (90 min) under UV light irradiation. Further, the photodegradation mechanisms of CAL were explored to find the reason behind the increased toxicity observed. Laser flash photolysis and quenching experiments showed that O₂^•- , ¹ O₂ , and ^• OH were mainly responsible for CAL photodegradation, together with ³ CAL* and e_aq^- . The 5 main photodegradation products were cinnamyl aldehyde, benzaldehyde, benzenepropanal, cinnamic acid, and toluene, as identified using gas chromatography-mass spectrometry and liquid chromatography-quadrupole-time-of-flight-mass spectrometry. Once exposed to air, CAL was found to be easily oxidized to cinnamyl aldehyde and subsequently to cinnamic acid by O₂^•- - or ¹ O₂ -mediated pathways, leading to increased toxicity. Benzaldehyde exhibited bioreactive toxicity, increasing the toxicity through ^• OH-mediated pathways. Theoretical prediction of skin irritation indicated that cinnamyl aldehyde (0.83), benzenepropanal (0.69), cinnamyl aldehyde (0.69), and benzaldehyde (0.70) were higher than CAL (0.63), which may cause a profound impact on an individual's health and well-being. Overall, the present study advances the understanding of the photodegradation processes and health impacts of fragrance ingredients. Environ Toxicol Chem 2021;40:2705-2714. © 2021 SETAC.

Cinnamyl Isobutyrate Decreases Plasma Glucose Levels and Total Energy Intake from a Standardized Breakfast: A Randomized, Crossover Intervention

SCOPE

Cinnamon is associated with anti-obesity effects, regulating food intake, improving plasma glucose levels and lipid profiles in vivo. In the present study, the impact of cinnamyl isobutyrate (CIB), one constituent of cinnamon, on ad libitum food intake from a standardized breakfast and outcome measures of hormonal regulation of appetite were investigated.

METHODS AND RESULTS

In this randomized, short-term crossover intervention study, a 75 g per 300 mL glucose solution solely (control) or supplemented with 0.45 mg CIB was administered to 26 healthy volunteers. Prior to and 2 h after receiving control or CIB treatment, subjective hunger perceptions were rated using a visual analog scale. Food intake from a standardized breakfast was assessed 2 h after treatments. Plasma peptide YY3-36 , glucagon-like-peptide1, ghrelin, and serotonin as well as plasma glucose and insulin were measured in blood samples drawn at fasting and 15, 30, 60, 90, and 120 min after treatment. CIB administration decreased total energy intake and delta area under curve plasma glucose by 4.64 ± 3.51% and 49.3 ± 18.5% compared to control treatment, respectively.

CONCLUSIONS

CIB, administered at a 0.45 mg bolus in 75 g glucose-water solution, decreased ad libitum energy intake from a standardized breakfast and postprandial plasma glucose levels.

Associated factors of widespread pattern of dermatitis among patch test population: 12-Year retrospective study

BACKGROUND/OBJECTIVE

Widespread dermatitis is often associated with diagnostic and therapeutic challenges. Multiple factors influence this widespread pattern of dermatitis. We aim to study the associated factors in patch-tested patients who presented with widespread pattern of dermatitis.

METHOD

This retrospective, case-control study was conducted on patients with dermatitis who were patch tested during January 2005 to December 2016. The demographic data, patient and family histories, diagnoses, and patch test findings were recorded and analyzed.

RESULTS

Of the 3201 included patients, 645 (20.2%) had widespread pattern of dermatitis. Being male, age >60, and history of either atopic dermatitis (AD) or metal allergy were significantly associated with the widespread dermatitis pattern. A multivariate analysis demonstrated that preservatives were the significant offending allergens, especially methylchloroisothiazolinone/methylisothiazolinone (MCI/MI), and methylisothiazolinone (MI) alone.

CONCLUSION

Widespread pattern of dermatitis is associated with gender, age, underlying atopic dermatitis and a history of metal allergy. Preservatives are the significant offending allergens of widespread dermatitis, especially MCI/MI, and MI alone. A thorough history taking and patch testing, including preservatives, are necessary to determine the cause of widespread pattern of dermatitis.

Fragrance allergic contact dermatitis

Fragrances are a common cause of allergic contact dermatitis in Europe and in North America. They can affect individuals at any age and elicit a spectrum of reactions from contact urticaria to systemic contact dermatitis. Growing recognition of the widespread use of fragrances in modern society has fueled attempts to prevent sensitization through improved allergen identification, labeling, and consumer education. This review provides an overview and update on fragrance allergy. Part 1 discusses the epidemiology and evaluation of suspected fragrance allergy. Part 2 reviews screening methods, emerging fragrance allergens, and management of patients with fragrance contact allergy. This review concludes by examining recent legislation on fragrances and suggesting potential additions to screening series to help prevent and detect fragrance allergy.

Polysensitization and increased susceptibility in contact allergy: a review

Genetic factors presumably play a role in contact allergy (CA). There is, however, a lack of conclusive evidence from clinical studies. This may be on account of the strongly competing or modifying impact of exogenous factors, namely the potency of allergens and the intensity of exposure, and the fact that - in principle - everybody can be sensitized. Regarding phenotype, in contrast, polysensitization (PS) seems to indicate a subset of individuals at greater risk. In human sensitization experiments with dinitrochlorobenzene, induction was facilitated in PS, and elicitation enhanced. Recent clinical epidemiological data, taking confounders for PS, such as age, sex, and other skin diseases into account, demonstrated the following: (i) PS was the greatest risk factor to be sensitized to a number of (even weak) index allergens, indicating higher susceptibility on the level of induction; (ii) patch test reactions in PS patients were generally stronger indicating higher susceptibility on the level of elicitation. These findings are complemented by reports on polymorphisms of TNF-alpha and IL-16 in PS patients. Future studies on the genetics of CA should be performed in subgroups with PS, focussing on polymorphisms relevant for CA-specific and nonspecific (inflammatory) processes.

Allergic contact dermatitis

The pathophysiology of ACD follows an intricate design and results in the characteristic, delayed inflammatory response. Although the astute physician may correctly diagnose ACD from its initial, classic history and presentation, alternative diagnoses should be considered and excluded. Patch testing performed with a relevant panel of contact allergens is the ultimate confirmatory test of ACD. Correctly identifying the inciting allergen permits appropriate personal avoidance. Corticosteroids remain the principal treatment options.

Fragrance material review on cinnamyl alcohol

A toxicologic and dermatologic review of cinnamyl alcohol when used as a fragrance ingredient is presented.

Fragrance material review on cinnamaldehyde

A toxicologic and dermatologic review of cinnamaldehyde when used as a fragrance ingredient is presented.

Cinnamic compound metabolism in human skin and the role metabolism may play in determining relative sensitisation potency

BACKGROUND

trans-Cinnamaldehyde and trans-cinnamic alcohol cause allergic contact dermatitis (ACD) in humans; cinnamaldehyde is a more potent sensitiser than cinnamic alcohol. These two chemicals are principal constituents of the European Standard 'Fragrance Mix', as used in patch testing diagnostics of sensitisation to fragrances by clinical dermatologists. As contact sensitisers are usually protein reactive compounds, it is hypothesised that cinnamic alcohol (not protein-reactive) is a 'prohapten' that requires metabolic activation, presumably by cutaneous oxidoreductases, to the protein-reactive cinnamaldehyde (a 'hapten'). It is postulated that cinnamaldehyde can be detoxified by aldehyde dehydrogenase (ALDH) to cinnamic acid and/or by alcohol dehydrogenase (ADH) to cinnamic alcohol. Hence, a variety of metabolic pathways may contribute to the relative exposures and hence sensitising potencies of cinnamic alcohol and cinnamaldehyde.

OBJECTIVE

To evaluate the extent of cinnamaldehyde and cinnamic alcohol metabolism in human skin and provide evidence for the role of cutaneous ADH and ALDH in such metabolism.

METHODS

The extent of cinnamic alcohol and aldehyde metabolism was investigated in human skin homogenates and sub-cellular fractions. A high performance liquid chromatography method was used for analysis of skin sample extracts. Studies were conducted in the presence and absence of the ADH/cytochrome P450 inhibitor 4-methylpyrazole and the cytosolic ALDH inhibitor, disulfiram.

RESULTS

Differential metabolism of cinnamic alcohol and cinnamaldehyde was observed in various subcellular fractions: skin cytosol was seen to be the major site of cinnamic compound metabolism. Significant metabolic inhibition was observed using 4-methylpyrazole and disulfiram in whole skin homogenates and cytosolic fractions only.

CONCLUSIONS

This study has demonstrated that cutaneous ADH and ALDH activities, located within defined subcellular compartments, play important roles in the activation and detoxification of CAlc and CAld in skin. Such findings are important to the development of computational hazard prediction tools for sensitisation (e.g. the DEREK program) and also to dermatologists in understanding observed interindividual differences, cross-reactivities or co-sensitisation to different cinnamic compounds in the clinic.

Evaluation of the role of contact sensitization and photosensitivity in the pathogenesis of poikiloderma of Civatte

BACKGROUND

Poikiloderma of the face and neck (Civatte) is a rather common, indolent, chronic dermatosis, most often affecting menopausal females. Cumulative excessive sun exposure, a phototoxic or a photoallergic reaction, hormonal changes of menopause and genetic factors have all been incriminated in its obscure aetiopathogenesis.

OBJECTIVE

To evaluate the role of contact sensitization and photosensitivity in the pathogenesis of poikiloderma of Civatte (PC).

METHODS

Thirty-two patients (24 females and eight males, age range 38-74 years) with PC were patch tested with the European standard series and the fragrance series, and were photopatch tested with the photoallergens series. Additionally, photo-testing with a monochromator was performed.

RESULTS

Thirteen of 32 patients (40.62%) had one or more positive reactions to allergens of the standard series. Eight patients (25%) had positive reactions to fragrance mix and/or Balsam of Peru, which are included in the standard series, or to allergens of the fragrance series. Nickel sulphate was the single most common cause of contact sensitization (18.75%) among our patients. Ninety-seven subjects, who were patch tested with the standard series for suspected allergic contact dermatitis of the face and/or neck, served as age, sex and site controls. Of these, nine (9.27%) had one or more positive reactions to fragrance compounds. Statistical analysis showed a statistically significant difference in the frequency of positive reactions to fragrances between the PC group and the control group (chi2 value = 3.91, P < 0.05). In contrast, none of the PC patients had a positive photopatch test for the allergens included in the photoallergens series. The estimated minimal erythemal dose for the PC group was in all cases within normal limits for all wavelengths of ultraviolet (UV) radiation examined.

CONCLUSIONS

Contact sensitization, mostly to perfume ingredients, may develop in PC, possibly playing a pathogenetic part, at least in a subset of patients. Despite negative results of photopatch testing, an allergic photo-contact reaction cannot be definitely excluded. PC seems not to be a photosensitivity disorder of the type of chronic actinic dermatitis. UV radiation-induced dermal connective tissue changes are the predominant histological feature of PC, leading to telangiectasia due to loss of vascular support. Reticular pigmentation may result from a delayed hypersensitivity reaction to perfume and/or cosmetic ingredients. Patch testing with the standard series and avoidance of documented allergens may be of value in patients with PC.

High-performance liquid chromatography method for the quantification of non-radiolabelled cinnamic compounds in analytes derived from human skin absorption and metabolism experiments

An isocratic high-performance liquid chromatography method has been developed for the quantification of the skin sensitisers trans-cinnamaldehyde and trans-cinnamic alcohol, and their cinnamic metabolites. The relative standard deviations (RSDs) between the gradients of eight sets of standard curves were 2.8, 3.1 and 1.9% for cinnamic alcohol, cinnamaldehyde and cinnamic acid, respectively. Sample analytes were derived from two series of experiments: in vitro full-thickness human skin absorption and metabolism studies and metabolism studies using human skin homogenates, with non-radiolabelled cinnamic compounds. Skin absorption and metabolism experiments were performed in the absence and presence of the alcohol dehydrogenase inhibitor, pyrazole. Samples from full-thickness skin absorption studies were analysed without extraction; cinnamic compounds from within skin were extracted into methanolic solutions using newly developed methods. The intra-assay RSDs ranged from 0.17 to 2.52% for cinnamic alcohol, 0.24 to 9.14% for cinnamaldehyde and 0.26 to 6.43% for cinnamic acid. The inter-assay RSDs for cinnamic alcohol, cinnamaldehyde and cinnamic acid, respectively, as determined from n=20 HPLC runs, were 2.10, 4.16 and 2.26%.

Release of markedly increased quantities of prostaglandin D2 from the skin in vivo in humans after the application of cinnamic aldehyde

BACKGROUND

Cinnamic aldehyde is a common fragrance additive in foods and various health and beauty products. Application of cinnamic aldehyde to the skin of humans can induce cutaneous vasodilatation characterized by erythema, urticaria, and stinging. Previous studies have suggested that prostaglandins (PGs) may mediate the vasodilation, but the causative PG has not been established. We have shown that cutaneous vasodilatation induced by compounds such as sorbic acid and methylnicotinate is mediated by PGD2.

OBJECTIVE

Our purpose was to determine whether cutaneous vasodilatation induced by cinnamic aldehyde is mediated by PGD2 in humans.

METHOD AND RESULTS

Topical application of 1% cinnamic aldehyde to the forearms of 3 human volunteers resulted in cutaneous flushing and 25- to 42-fold increases in the levels of the major circulating metabolite of PGD2, 9alpha, 11beta-PGF2, in blood drawn from the antecubital vein draining the treated sites. There was no increase in other vasodilatory mediators, including PGE2, PGI2, or histamine. The release of PGD2 was concentration dependent. Cutaneous vasodilatation and PGD2 release were markedly decreased by the administration of aspirin, but were not significantly altered by pretreatment with the selective cyclooxygenase-2 inhibitor rofecoxib, suggesting that the formation of PGD2 is dependent on cyclooxygenase-1.

CONCLUSION

The cutaneous vasodilatation induced by cinnamic aldehyde is mediated to a large extent by the release of PGD2 from a cellular source in the skin.

Human skin absorption and metabolism of the contact allergens, cinnamic aldehyde, and cinnamic alcohol

trans-Cinnamaldehyde and trans-cinnamic alcohol have been commonly reported to cause allergic contact dermatitis (ACD) in humans. Cinnamaldehyde is a more potent skin sensitizer than cinnamic alcohol. It has been hypothesized that cinnamic alcohol is a "prohapten" that requires metabolic activation, presumably by oxidoreductase enzymes such as alcohol dehydrogenase (ADH) or cytochrome P450 2E1 (CYP2E1), to the protein-reactive cinnamaldehyde (a hapten). In this study, the in vitro percutaneous absorption and metabolism of cinnamaldehyde and cinnamic alcohol (78 micromol dose) has been examined using freshly excised, metabolically viable, full-thickness breast and abdomen skin from six female donors. Penetration rates and total cumulative recoveries of cinnamic compounds that were present in receptor fluid, extracted from within the skin, evaporated from the skin surface, or remained unabsorbed on the skin surface after 24 h were quantified by reversed-phase high-performance liquid chromatography. Biotransformation of cinnamaldehyde to both cinnamic alcohol and cinnamic acid was observed. Topically applied cinnamic alcohol was converted to cinnamaldehyde (found on the skin surface only) and cinnamic acid. To establish whether these biotransformations were enzymatic, experiments were performed in the absence and presence of varying concentrations (80-320 micromol) of the ADH/CYP2E1 inhibitors pyrazole or 4-methylpyrazole. The observation that pyrazole significantly reduced (p < 0.05) the total penetration of cinnamic metabolites into receptor fluid, following either cinnamaldehyde or cinnamic alcohol treatment, but did not significantly affect parent chemical penetration, suggests that we are measuring cutaneous metabolic products of ADH activity. The skin absorption and metabolism of cinnamaldehyde and cinnamic alcohol will play an important role in the manifestation of ACD following topical exposure to these compounds.