Hydroxyisohexyl 3-cyclohexene carboxaldehyde- known as Lyral®: quantitative aspects and risk assessment of an important fragrance allergen

Delayed-Type Hypersensitivity to Fragrance Materials in a Select North American Population

BACKGROUND

In published reports from Europe, 3- and 4-(4-hydroxy-4-methylpentyl)cyclohexene-1-carboxaldehyde (HMPCC) (Lyral) has been described as a common cause of allergic contact dermatitis (ACD). In Europe, the rates of reaction to HMPCC among patients undergoing patch testing for suspected ACD have varied from 1.2 to 17.0%, depending on the country. Data on the incidence of sensitivity to HMPCC among North Americans with suspected ACD have not been reported.

OBJECTIVES

The goals of this study were (1) to assess the incidence of delayed-type hypersensitivity reactions to HMPCC among patients undergoing patch testing for evaluation of eczematous dermatitis at six centers throughout North America; (2) to determine the most appropriate concentration of HMPCC to use in performing patch tests; and (3) to compare and contrast the incidence rates for HMPCC hypersensitivity to those for other fragrance materials screened with the North American Contact Dermatitis Group (NACDG) screening tray, which includes fragrance mix, Myroxilon pereirae (balsam of Peru), cinnamic aldehyde, ylang ylang oil, jasmine absolute, and tea tree oil.

METHODS

This report represents the prospective multicenter data on patients tested with the fragrance-related allergens on the NACDG standard screening tray and with HMPCC at 5%, 1.5%, and 0.5% concentrations in petrolatum. Statistical analyses were performed with Student's t-test (two tailed) and the chi-square test.

RESULTS

Data from 1,603 patients evaluated at five US sites and one Canadian site were analyzed. Most patients (87.8%) were Caucasian. The majority (67%) were women, and 26.2% had a history consistent with atopic dermatitis. The patients ranged in age from 1 to 88 years, and the mean +/- standard deviation was 46.3 +/- 16.5 years. Myroxilon pereirae (balsam of Peru) and fragrance mix were the most frequent patch-test-positive fragrance allergens (6.6% and 5.9%, respectively). Cinnamic aldehyde (1.7%), ylang ylang oil (0.6%), jasmine absolute (0.4%), HMPCC (0.4% for 5% HMPCC, 0.3% for 1.5% HMPCC, and 0.2% for 0.5% HMPCC), and tea tree oil (0.3%) less frequently yielded positive reactions. Men were more likely than women to be allergic to cinnamic aldehyde. Women were more likely than men to be allergic to jasmine absolute. Atopic patients were no more likely to react to fragrance materials than were nonatopic patients. Patients who reacted to jasmine absolute tended to be older than the general population whereas those who reacted to tea tree oil tended to be younger than the general population. There were no other demographic differences between patients who reacted to a given fragrance material and the entire population studied. Testing with fragrance mix and balsam of Peru failed to identify the majority of patients in this study who were found to be sensitized to jasmine absolute, HMPCC, or tea tree oil.

CONCLUSION

HMPCC is an uncommon allergen in the North American population. We recommend testing with 5% HMPCC in petrolatum for those patients suspected of having a fragrance allergy.

Fragrance contact dermatitis in Korea: a joint study

The purpose of this study is to determine the frequency of responses to selected fragrances in patients with suspected fragrance allergy and to evaluate the risk factors. 9 dermatology departments of university hospitals have participated in this study for the past 1 year. To determine allergic response to fragrances, 18 additional fragrances in addition to the Korean standard and a commercial fragrance series were patch-tested in patients with suspecting cosmetic contact dermatitis. Over 80% of the patients were women, and the most common site was the face. Cinnamic alcohol and sandalwood oil (Santalum album L.) showed high frequencies of positive responses. Of the specific fragrances, ebanol, alpha-isomethyl-ionone (methyl ionone-gamma) and Lyral (hydroxyisohexyl 3-cyclohexane carboxdaldehyde) showed high positive responses. We compared the results obtained during this study with those of other studies and concluded that including additional fragrance allergens may be useful for the detection of fragrance allergy.

Patch testing with a new fragrance mix detects additional patients sensitive to perfumes and missed by the current fragrance mix

The currently used 8% fragrance mix (FM I) does not identify all patients with a positive history of adverse reactions to fragrances. A new FM II with 6 frequently used chemicals was evaluated in 1701 consecutive patients patch tested in 6 dermatological centres in Europe. FM II was tested in 3 concentrations - 28% FM II contained 5% hydroxyisohexyl 3-cyclohexene carboxaldehyde (Lyral), 2% citral, 5% farnesol, 5% coumarin, 1% citronellol and 10%alpha-hexyl-cinnamic aldehyde; in 14% FM II, the single constituents' concentration was lowered to 50% and in 2.8% FM II to 10%. Each patient was classified regarding a history of adverse reactions to fragrances: certain, probable, questionable, none. Positive reactions to FM I occurred in 6.5% of the patients. Positive reactions to FM II were dose-dependent and increased from 1.3% (2.8% FM II), through 2.9% (14% FM II) to 4.1% (28% FM II). Reactions classified as doubtful or irritant varied considerably between the 6 centres, with a mean value of 7.2% for FM I and means ranging from 1.8% to 10.6% for FM II. 8.7% of the tested patients had a certain fragrance history. Of these, 25.2% were positive to FM I; reactivity to FM II was again dose-dependent and ranged from 8.1% to 17.6% in this subgroup. Comparing 2 groups of history - certain and none - values for sensitivity and specificity were calculated: sensitivity: FM I, 25.2%; 2.8% FM II, 8.1%; 14% FM II, 13.5%; 28% FM II, 17.6%; specificity: FM I, 96.5%; 2.8% FM II, 99.5%; 14% FM II, 98.8%; 28% FM II, 98.1%. 31/70 patients (44.3%) positive to 28% FM II were negative to FM I, with 14% FM II this proportion being 16/50 (32%). In the group of patients with a certain history, a total of 7 patients were found reacting to FM II only. Conversely, in the group of patients without any fragrance history, there were significantly more positive reactions to FM I than to any concentration of FM II. In conclusion, the new FM II detects additional patients sensitive to fragrances missed by FM I; the number of false-positive reactions is lower with FM II than with FM I. Considering sensitivity, specificity and the frequency of doubtful reactions, the medium concentration, 14% FM II, seems to be the most appropriate diagnostic screening tool.

Clinical update on contact allergy

PURPOSE OF REVIEW

The aim of this article is to review recent findings in contact allergy, regarding clinical research.

RECENT FINDINGS

The biocide methyldibromo glutaronitrile was identified to be an important sensitizer. Subsequently, it was banned from leave-on cosmetics in the European Union. Another group of important allergens that have been studied extensively included the fragrances oak moss absolute, isoeugenol, hydroxyisohexyl 3-cyclohexene carboxaldehyde and farnesol. A new fragrance mix II has been developed for standard testing, which includes the two latter compounds. Dose response studies have demonstrated broad individual variation of elicitation thresholds, dependent on the allergen concentration during induction, and other factors. Some unsuspected routes of exposure to allergens include oral, inhalational, connubial or airborne contact. Experimental studies provide a classification of newly introduced chemicals; increasingly, the local lymph node assay is supplementing and potentially replacing the guinea pig maximization test. Recent advances in occupational contact allergy include, for example, some attempts to improve diagnostics for epoxy resin and other plastic, glue, and cutting fluid components.

SUMMARY

Constant awareness for new allergens, confirmed by critical evaluation, standardization of patch test materials, and the identification of temporal patterns and subgroups at risk will improve both the diagnosis and prevention of allergic contact dermatitis.

Patch testing with a new fragrance mix - reactivity to the individual constituents and chemical detection in relevant cosmetic products

A new fragrance mix (FM II), with 6 frequently used chemicals not present in the currently used fragrance mix (FM I), was evaluated in 6 dermatological centres in Europe, as previously reported. In this publication, test results with the individual constituents and after repeated open application test (ROAT) of FM II are described. Furthermore, cosmetic products which had caused a contact dermatitis in patients were analysed for the presence of the individual constituents. In 1701 patients, the individual constituents of the medium (14%) and the highest (28%) concentration of FM II were simultaneously applied with the new mix at 3 concentrations (break-down testing for the lowest concentration of FM II (2.8%) was performed only if the mix was positive). ROAT was performed with the concentration of the FM II which had produced a positive or doubtful (+ or ?+) patch test reaction. Patients' products were analysed for the 6 target compounds by gas chromatography-mass spectrometry (GC-MS).

RESULTS

50 patients (2.9%) showed a positive reaction to 14% FM II and 70 patients (4.1%) to 28% FM II. 24/50 (48%) produced a positive reaction to 1 or more of the individual constituents of 14% FM II and 38/70 (54.3%) to 28% FM II, respectively. If doubtful reactions to individual constituents are included, the break-down testing was positive in 74% and 70%, respectively. Patients with a positive reaction to 14% FM II showed a higher rate of reactions to the individual constituent of the 28% FM II: 36/50 (72%). Positive reactions to individual constituents in patients negative to FM II were exceedingly rare. If doubtful reactions are regarded as negative, the sensitivity, specificity, positive predictive value and negative predictive value for the medium concentration of FM II towards at least 1 individual constituent was 92.3% (exact 95% confidence interval 74.9-99.1%), 98.4% (97.7-99.0%), 48% (33.7-62.6%) and 99.9% (99.6-"100.0%), respectively. For the high concentration, the figures were very similar. The frequency of positive reactions to the individual constituents in descending order was the same for both FM II concentrations: hydroxyisohexyl 3-cyclohexene carboxaldehyde (Lyral) > citral > farnesol > citronellol > alpha-hexyl-cinnamic aldehyde (AHCA). No unequivocally positive reaction to coumarin was observed. Lyral) was the dominant individual constituent, with positive reactions in 36% of patients reacting to 14% FM II and 37.1% to 28% FM II. 5/11 patients developed a positive ROAT after a median of 7 days (range 2-10). The 5 patients with a doubtful or negative reaction to 28% FM II were all ROAT negative except 1. There were 7 patients with a certain fragrance history and a positive reaction to either 28% or 14% FM II but a negative reaction to FM I. Analysis with GC-MS in a total of 24 products obtained from 12 patients showed at least 1-5 individual constituents per product: Lyral (79.2%), citronellol (87.5%), AHCA (58.3%), citral (50%) and coumarin (50%). The patients were patch test positive to Lyral, citral and AHCA. In conclusion, patients with a certain fragrance history and a negative reaction to FM I can be identified by FM II. Testing with individual constituents is positive in about 50% of cases reacting to either 14% or 28% FM II.

Quantitative patch and repeated open application testing in methyldibromo glutaronitrile-sensitive patients

Contact allergy to methyldibromo glutaronitrile (MDBGN), often combined with phenoxyethanol (PE) (e.g., Euxyl K 400), increased throughout the 1990s in Europe. Consequently, in 2003, the European Commission banned its use in leave-on products, where its use concentration was considered too high and the non-sensitizing use concentration as yet unknown. The 2 objectives of the study are (a) to find a maximum non-eliciting concentration in a leave-on product in MDBGN/PE-sensitized patients, which could possibly also be considered safe regarding induction and (b) to find the best patch test concentration for MDBGN. We, therefore, performed a use-related test (ROAT) in patients sensitized to MDBGN/PE (n = 39) with 3 concentrations of MDBGN/PE (50, 100 and 250 p.p.m. MDBGN, respectively). A subset of these patients (n = 24) was later patch-tested with various concentrations (0.1, 0.2, 0.3 and 0.5% MDBGN, respectively). 15 patients (38%, 95% confidence interval (CI) = 23-55%) had a negative and 24 (62%; 95% CI = 45-77%) a positive overall repeated open application test (ROAT) result. 13 reacted to the lowest (50 p.p.m.), 8 to the middle (100 p.p.m.) and 3 to the highest concentration (250 p.p.m.) only. In those 13 reacting to the lowest ROAT concentration, dermatitis developed within a few days (1-7). The strength of the initial and the confirmatory patch test result, respectively, and the outcome of the ROAT were positively associated. Of the 24 patients with a use and confirmatory patch test, 15 reacted to 0.1% MDBGN, 16 to 0.2%, 17 to 0.3% and 22 to 0.5%. With the patch test concentration of 0.5%, the number of ROAT-negative patients but patch-test-positive patients increases considerably, particularly due to + reactions. A maximum sensitivity of 94% (95% CI = 70-100%) is reached with a patch test concentration of 0.2%, and is not further improved by increasing the concentration. However, the specificity decreases dramatically from 88 (95% CI = 47-100%) with 0.2% to a mere 12.5% (95% CI = 0-53%) with 0.5%. It can be concluded (a) that for MDBGN 0.2% is very likely the best patch test concentration and (b) that 50 p.p.m. in a leave-on product can elicit contact dermatitis in sensitized persons. We were, therefore, unable to find a safe, still microbicidal, concentration for leave-on products. By contrast, with other contact allergens, dose-response use tests may be able to identify a non-eliciting concentration, which could give valuable clues to a non-inducing (i.e., safe) concentration in products.

Methyldibromo glutaronitrile contact allergy: effect of single versus repeated daily exposure

Some types of cosmetic products such as hand soaps and creams are commonly used several times a day, especially in occupational use situations. Little has experimentally been shown of how the daily frequency of the application of an allergen in a product influences the allergic response. This study investigates the allergic responses elicited in presensitized individuals when exposed to a specific amount of allergen applied either in 1 application per day or distributed over 4 applications per day. As model allergen, the cosmetic preservative methyldibromo glutaronitrile (MDBGN) is used. 19 contact allergic individuals and 12 controls participated in a double-blind, randomized use test. To areas on the forearms were applied 2 drops either once daily of a solution containing 0.04% MDBGN or 4 times a day of a solution containing 0.01% MDBGN. 14 of 19 patients developed dermatitis following the application of approximately equal amounts of MDBGN on both arms. Controls were negative. In this experiment, applications of 0.04% MDBGN once daily or 0.01% MDBGN 4 times daily had, in a use test, approximately equal capabilities of provoking allergic contact dermatitis. This adds new knowledge to the risk assessment and regulation of cosmetic allergens. However, these results may be highly allergen dependent, and further studies are needed before more general conclusions can be made.

Thresholds of elicitation depend on induction conditions. Could low level exposure induce sub-clinical allergic states that are only elicited under the severe conditions of clinical diagnosis?

While numerous studies have examined dose/response relationships occurring in the experimental induction of contact allergic dermatitis, fewer have examined the effects of varying the doses of both induction and challenge. Recently published studies have however done this and they all show the same remarkable observation: the threshold of elicitation decreases as the doses used to induce the allergy increase. This has important implications. One is that it may be more complicated to determine clear threshold doses below which allergic responses are not seen. It is also proposed that normal exposure to weak allergens such as some fragrance materials may induce "sub-clinical" allergic states which will not be elicited under these same exposure conditions but which may become apparent under the more severe conditions of clinical diagnosis. This may explain why the prevalence of Patch test reactions to some fragrance materials is apparently increasing in the absence of any clearly documented "epidemic" of consumer complaints.

Chloroatranol, an extremely potent allergen hidden in perfumes: a dose-response elicitation study

Oak moss absolute is a long-known, popular natural extract widely used in perfumes. It is reported as the cause of allergic reactions in a significant number of those with perfume allergy. Oak moss absolute has been the target of recent research to identify its allergenic components. Recently, chloroatranol, a hitherto unknown fragrance allergen, was identified in oak moss absolute. The objective was to assess the clinical importance of chloroatranol as a fragrance allergen by characterizing its elicitation profile. 13 patients previously showing a positive patch test to oak moss absolute and chloroatranol were included, together with a control group of 10 patients without sensitization to either of the 2 materials. A serial dilution patch test was performed on the upper back with concentrations ranging from 200 to 0.0063 p.p.m. of chloroatranol in ethanol. Simultaneously, the participant performed an open test simulating the use of perfumes on the volar aspect of the forearms in a randomized and double-blinded design. A solution with 5 p.p.m. chloroatranol was used for 14 days, and, in case of no reaction, the applications were continued for another 14 days with a solution containing 25 p.p.m. All test subjects (13/13) developed an allergic reaction at the site of application of the solution containing chloroatranol. Among them, 12/13 (92%) gave a positive reaction to the 5 p.p.m. solution and 1 to 25 p.p.m. None of the controls reacted (P < 0.001). The use test was terminated at median day 4. The dose eliciting a reaction in 50% of the test subjects at patch testing was 0.2 p.p.m. In conclusion, the hidden exposure to a potent allergen widely used in perfumes has caused a highly sensitized cohort of individuals. Judged from the elicitation profile, chloroatranol is the most potent allergen present in consumer products today.