Paradox allergen: Lanolin allergy investigated for improved patch testing

31 May 2023 --- Columbia University Irving Medical Center researchers have analyzed factors surrounding the allergenicity of lanolin – a popular emollient and moisturizer used in cosmetics – to determine how common its allergy is in the general population and identify the appropriate screening methods.

Lanolin’s allergenicity remains controversial and the efficacy of common patch testing to detect lanolin allergy is often disputed. The substance and its derivatives are designed for topical use on skin, lips, nails and hair, as an ocular emollient and for many industrial purposes. 

While the researchers describe lanolin as a “weak sensitizer,” they identify special populations for which the concern for lanolin allergy may be greater. These include people with stasis dermatitis/chronic venous insufficiency, chronic leg ulcer or perianal and genital dermatitis, atopic dermatitis patients, children and the elderly.

“Detection of lanolin allergy by patch testing is challenging because ‘allergic’ patients may tolerate lanolin on healthy skin yet develop contact dermatitis when products containing lanolin are used on inflamed skin,” explains Dr. Anthony Gaspari from Sidney Kimmel Medical College of Thomas Jefferson University, US, and editor-in-chief of Dermatitis. 

Contact allergen of the year
Lanolin, termed a “paradoxical allergen” by researchers, is a complex mixture of high molecular weight esters, aliphatic alcohols, sterols, fatty acids and hydrocarbons. 

The purification of crude lanolin into lanolin wax and the processing of this wax into various derivatives began in 1882 and continue to this day with newer highly purified anhydrous lanolins.The European Commission’s new draft of Regulation 1223/2009 lists 56 ingredients that have allergenic properties. 

The potential for lanolin to cause contact allergy in humans is well documented and the phenomenon of lanolin allergenicity is the focus of the Contact Allergen of the Year article in the peer-reviewed journal Dermatitis.

The study highlights that the frequency of developing a contact allergy to lanolin in the European population, in particular, is roughly 0.4% and there are high-risk concomitant conditions such as stasis dermatitis, leg ulcers, perianal/genital dermatitis and atopic dermatitis. 

Because lanolin is commonly derived from sheep’s wool, the Vegan Society previously advised that a lack of regulations surrounding scientific terms for ingredients means that even when shoppers check the ingredient list for animal-based products before purchasing, they may lack the knowledge to help them make an informed choice.

Patch testing
Controversy about its allergenicity began in the 1920s and remains an issue. The most appropriate patch test preparations 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, the researchers state. 

In the US, non-Hispanic white patients are likelier than their non-Hispanic black counterparts to be lanolin allergic.

The allergenicity of cosmetic compounds remains a salient issue at the top of mind of regulators. A recent study found that personal skin care products applied topically can increase the risk of food allergies based on their ingredients. Thus, the researchers highlight that parents must be aware of the allergenic nature of pediatric skin care products used on children.

Among other developments, a new draft by the European Commission lists 56 ingredients to be added to Regulation 1223/2009, summing-up more than 80 fragrances, individually required to be declared as allergens “if their concentration exceeds 0.001% in leave-on products and 0.01% in rinse-off products.” 

By Inga de Jong

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