'Hidden' fragrance compound can cause contact allergy

In accordance with the EU Cosmetics Directive, makeup, ointments, shampoo, deodorants, toothpaste and other products must contain a declaration of ingredients in order for consumers to avoid the substances to which they are allergic.

Cause of contact allergy Linalyl acetate, a fragrance chemical, is an exception -- it is not listed in the Directive and does not have to appear in declarations of ingredients. The substance is mildly allergenic. New studies at Sahlgrenska Academy have found that it can react with oxygen in the air to form strongly allergenic hydroperoxides. Thus, linalyl acetate may be a common cause of contact allergy.

Allergic reactions The study included 1,717 subjects who were being assessed for eczema related to contact allergy. Approximately 2% of them had allergic reactions to oxidized linalyl acetate.

"That may seem like a small percentage," says Lina Hagvall, a researcher at the University of Gothenburg. "But it is approximately the same result as for the fragrance compounds listed in the Cosmetics Directive."

Broad range of tests The subjects who reacted to oxidized linalyl acetate were also exposed to other fragrance compounds that are part of routine testing these days. A total of 57% of them had no allergic reaction.

"The trials suggest that a broad range of tests is required to detect contact allergies to fragrance compounds," Dr. Hagvall says. "Current tests do not identify the majority of people who have contact allergy to oxidized linalyl acetate."

Hard to avoid Because the substance is not declared on cosmetic products, consumers have trouble avoiding it, which can turn allergic eczema into a more severe, long-term condition.

According to the researchers, the study findings should lead to inclusion of oxidized linalyl acetate among the fragrance compounds used for diagnosis of contact allergy. The substance should also appear in the declaration of ingredients for cosmetic products.