Compendium of the most significant studies with reference to properties, intake, effects.

Mowitz M, Svedman C, Zimerson E, Bruze M. Usage tests of oak moss absolutes containing high and low levels of atranol and chloroatranol. Acta Derm Venereol. 2014 Jul;94(4):398-402. doi: 10.2340/00015555-1725.

Abstract. Atranol and chloroatranol are strong contact allergens in oak moss absolute, a lichen extract used in perfumery. Fifteen subjects with contact allergy to oak moss absolute underwent a repeated open application test (ROAT) using solutions of an untreated oak moss absolute (sample A) and an oak moss absolute with reduced content of atranol and chloroatranol (sample B). All subjects were in addition patch-tested with serial dilutions of samples A and B. Statistically significantly more subjects reacted to sample A than to sample B in the patch tests. No corresponding difference was observed in the ROAT, though there was a significant difference in the time required to elicit a positive reaction. Still, the ROAT indicates that the use of a cosmetic product containing oak moss absolute with reduced levels of atranol and chloroatranol is capable of eliciting an allergic reaction in previously sensitised individuals.

Johansen JD, Andersen KE, Svedman C, Bruze M, Bernard G, Giménez-Arnau E, Rastogi SC, Lepoittevin JP, Menné T. Chloroatranol, an extremely potent allergen hidden in perfumes: a dose-response elicitation study. Contact Dermatitis. 2003 Oct;49(4):180-4. doi: 10.1111/j.0105-1873.2003.0214.x. 

Abstract. 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.

Geier J, Brans R. How common is fragrance allergy really?. Hautarzt. 2020 Mar;71(3):197-204. German. doi: 10.1007/s00105-019-04534-w. 

Abstract. Background: Fragrances are regarded as the most common contact allergens after nickel. In this context, the frequency of positive patch test reactions to fragrance mix is often presented as proof. According to EU regulation No. 1223/2009, 26 fragrances that are regarded as significant allergens have to be declared on cosmetic products. Objectives: The frequency of patch test reactions to fragrances and differentiation between frequently and rarely sensitizing fragrances were evaluated....Discussion: The decline of positive test reactions to the fragrance mixes is mainly due to the reduced use of oakmoss containing atranol and chloroatranol, and HICC. Use of these substances in cosmetic products was prohibited within the EU starting in August 2019. Therefore, a further decline of the sensitization frequencies can be expected. A differentiated consideration of the individual fragrances under allergological aspects is urgently required.

Johansen JD, Bernard G, Giménez-Arnau E, Lepoittevin JP, Bruze M, Andersen KE. Comparison of elicitation potential of chloroatranol and atranol--2 allergens in oak moss absolute. Contact Dermatitis. 2006 Apr;54(4):192-5. doi: 10.1111/j.0105-1873.2006.00814.x.

Abstract. Chloroatranol and atranol are degradation products of chloroatranorin and atranorin, respectively, and have recently been identified as important contact allergens in the natural fragrance extract, oak moss absolute. Oak moss absolute is widely used in perfumery and is the cause of many cases of fragrance allergic contact dermatitis. Chloroatranol elicits reactions at very low levels of exposure. In oak moss absolute, chloroatranol and atranol are present together and both may contribute to the allergenicity and eliciting capacity of the natural extract. In this study, 10 eczema patients with known sensitization to chloroatranol and oak moss absolute were tested simultaneously to a serial dilution of chloroatranol and atranol in ethanol, in equimolar concentrations (0.0034-1072 microM). Dose-response curves were estimated and analysed by logistic regression. The estimated difference in elicitation potency of chloroatranol relative to atranol based on testing with equimolar concentrations was 217% (95% confidence interval 116-409%). Both substances elicited reactions at very low levels of exposure. It is concluded that the differences in elicitation capacity between the 2 substances are counterbalanced by exposure being greater to atranol than to chloroatranol and that both substances contribute to the clinical problems seen in oak moss absolute-sensitized individuals.