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

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).

To investigate whether chemically modified extracts of oak moss produce positive patch test reactions in previously sensitized subjects.

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.

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.

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.