Lanolin was announced as the Allergen of the Year by the American Contact Dermatitis Society in March 2023.1 However, allergic contact dermatitis (ACD) to lanolin remains a matter of fierce debate among dermatologists. Herein, we discuss this important contact allergen, emphasizing the controversy behind its allergenicity and nuances to consider when patch testing.
What is Lanolin?
Lanolin is a greasy, yellow, fatlike substance derived from the sebaceous glands of sheep. It is extracted from wool using an intricate process of scouring with dilute alkali, centrifuging, and refining with hot alkali and bleach.2 It is comprised of a complex mixture of esters, alcohols, sterols, fatty acids, lactose, and hydrocarbons.3
The hydrophobic property of lanolin helps sheep shed water from their coats.3 In humans, this hydrophobicity benefits the skin by retaining moisture already present in the epidermis. Lanolin can hold as much as twice its weight in water and may reduce transepidermal water loss by 20% to 30%.4-6 In addition, lanolin maintains tissue breathability, which supports proper gas exchange, promoting wound healing and protecting against infection.3,7
Many personal care products (PCPs), cosmetics, and topical medicaments contain lanolin, particularly products marketed to help restore dry cracked skin. The range of permitted concentrations of lanolin in over-the-counter products in the United States is 12.5% to 50%.3 Lanolin also may be found in industrial goods. The Table provides a comprehensive list of common items that may contain lanolin.1,3,8,9
A Wolf in Sheep’s Clothing?
Despite its benefits, lanolin is a potential source of ACD. The first reported positive patch test (PPT) to lanolin worldwide was in the late 1920s.10 Subsequent cases of ACD to lanolin were described over the next 30 years, reaching a peak of recognition in the latter half of the 20th century with rates of PPT ranging from 0% to 7.4%, though the patient population and lanolin patch-test formulation used differed across studies.9 The North American Contact Dermatitis Group observed that 3.3% (1431/43,691) of patients tested from 2001 to 2018 had a PPT to either lanolin alcohol 30% in petrolatum (pet) or Amerchol L101 (10% lanolin alcohol dissolved in mineral oil) 50% pet.11 Compared to patients referred for patch testing, the prevalence of contact allergy to lanolin is lower in the general population; 0.4% of the general population in Europe (N=3119) tested positive to wool alcohols 1.0 mg/cm2 on the thin-layer rapid use Epicutaneous (TRUE) test.12
Allergic contact dermatitis to lanolin is unrelated to an allergy to wool itself, which probably does not exist, though wool is well known to cause irritant contact dermatitis, particularly in atopic individuals.13
Who Is at Risk for Lanolin Allergy?
In a recent comprehensive review of lanolin allergy, Jenkins and Belsito1 summarized 4 high-risk subgroups of patients for the development of lanolin contact allergy: stasis dermatitis, chronic leg ulcers, atopic dermatitis (AD), and perianal/genital dermatitis. These chronic inflammatory skin conditions may increase the risk for ACD to lanolin via increased exposure in topical therapies and/or increased allergen penetration through an impaired epidermal barrier.14-16 Demographically, older adults and children are at-risk groups, likely secondary to the higher prevalence of stasis dermatitis/leg ulcers in the former group and AD in the latter.1