Lanolin is a complex and varying mixture of high molecular weight esters, aliphatic alcohols, sterols, fatty acids, and hydrocarbons, but the allergic components are mainly the free lanolin alcohols, especially alkanediols, said Donald V. Belsito, MD, professor of dermatology, Columbia University, New York, who announced the Allergen of the Year at the society’s annual meeting.
Criteria for selection can include a known allergen with a new twist or increasing frequency or a newly reported allergen with mini-epidemics that may have been missed for years, Dr. Belsito said.
“The prevalence and severity of allergy to ‘lanolin’ have been hotly debated” since a potential case was first reported in the 1920s, wrote Dr. Belsito and Blair A. Jenkins, MD, PhD, a dermatology resident at New York–Presbyterian Hospital, Columbia Campus, in a review published in Dermatitis.
“ ‘Lanolin’ is indeed a paradox allergen,” wrote Dr. Jenkins and Dr. Belsito. “The most appropriate patch test preparation(s) for detecting allergy remain disputed. Detection of lanolin-induced contact dermatitis in diseased skin by patch testing on normal skin may lead to false negative results.”
And those who test positive for a lanolin allergy on diseased skin may be able to use lanolin products on normal skin, they wrote.
“From my perspective, this was a timely year to think about lanolin, as there is significant ongoing controversy about whether it is allergenic,” Dr. Jenkins said in an interview. “Numerous companies market lanolin-containing topicals as safe and effective emollients,” she said.
Medical grade and highly purified anhydrous lanolin, which contain less than 2.5% and less than 1.5% of free alcohols, respectively, can still elicit or induce a contact allergy, Dr. Belsito said in his presentation. Hydrogenated lanolin has shown more allergenicity than lanolin alcohol, while lanolin wax, lanolin acid, and lanolin esters possess lower allergenicity than lanolin alcohol, he said.
Notably, modern wool textiles do not contain lanolin, and lanolin-allergic patients need not avoid wool, Dr. Belsito added.
Amerchol L-101, a common trade name on products containing lanolin, contains 10% wool wax alcohols obtained from the hydrolysis of wool fat dissolved in mineral oil at a 1:1 ratio, said Dr. Belsito. He recommended testing lanolin alcohols (in 30% petrolatum) and Amerchol L-101 (in 50% petrolatum) simultaneously with or without other lanolin derivatives and/or the patient’s products in cases of possible allergy, he said.
Consider high-risk groups
Current evidence suggests that the prevalence of contact allergy in the western European population is 0.4%, wrote Dr. Jenkins and Dr. Belsito.
Although the frequency of lanolin allergy is relatively low, certain conditions convey greater risk, such as stasis dermatitis, leg ulcers, perianal/genital dermatitis, and atopic dermatitis, they wrote. Older adults and children are at increased risk because they are more likely to have these conditions. Demographic data also suggest that lanolin allergy is more common in non-Hispanic Whites than in non-Hispanic Blacks, they wrote.
Looking ahead, “I think further exploration of allergy across different skin types and ethnicities is warranted,” Dr. Jenkins said. “Further investigation of ideal [lanolin] allergens for patch testing is also needed.”
Dr. Jenkins and Dr. Belsito said they had no relevant financial conflicts to disclose.