Is a low content in atranol/chloroatranol safe in oak moss-sensitized individuals?

Background: Chloroatranol and atranol are degradation products of chloroatranorin and atranorin, respectively, and have been identified as important contact allergens in oak moss absolute (Evernia prunastri). Objectives: To investigate whether chemically modified extracts of oak moss produce positive patch test reactions in previously sensitized subjects. Methods: A sample of oak moss was treated by a polymer‐based method to reduce the content of the two main allergens, namely atranol and chloroatranol, from 3.4% to less than 75 p.p.m. and from 1.8% to less than 25 p.p.m., respectively. Fourteen subjects with positive reactions to oak moss from Trolab and/or Chemotechnique were patch tested to this sample, diluted 1% in petrolatum. Results: The chemically modified sample reacted negatively in six but gave still positive reactions in eight subjects, with the same intensity as the commercially available oak moss patch test materials. Conclusions: Polymer‐based treatment of oak moss extract reduces the allergenic elicitation potential in previously sensitized individuals only to a minor extent. The residual concentrations of atranol and chloroatranol being less than 75 p.p.m. and 25 p.p.m., respectively, are unsafe for the consumer.