Hjorth and Trolle-Lassen hypothesized that the use of antioxidants may stabilize possible allergens and reduce the allergenicity of lanolin. They patch-tested 13 patients found previously to have positive reactions to lanolin with anhydrous lanolin, salicylic acid (5%) in lanolin, and three different preparations of lanolin plus antioxidants (2% p-aminophenol, 5% pyrogallol, 2% p-phenylenediamine). All 13 subjects had positive reactions to both antioxidant-free lanolin preparations whereas only 3 of the 13 reacted to p-aminophenol in lanolin. No patients reacted to pyrogallol or p-phenylenediamine in lanolin. Importantly, all three of these antioxidants are known contact allergens. To our knowledge, these antioxidants have not been used in commercial lanolin products to decrease sensitization rates.
In 1981, Clark and colleagues showed that reducing the free alcohol content of lanolin decreased its sensitizing potential. A large portion of the free alcohols and most of the detergent were removed from anhydrous lanolin. Thirty-four patients previously found to be “lanolin sensitive” were patch-tested with the purified lanolin. When the free alcohol content of lanolin was reduced to 1.5% and the detergent content was reduced to 0.01%, there were no positive reactions. Subsequently, these same 34 individuals were then retested with sequentially higher concentrations of free alcohols. Concentrations of 5% wool alcohols yielded positive reactions in 41% of subjects while 59% reacted to 10% wool alcohols. Increasing the alcohol content to 20% and 30%, however, did not significantly further increase the positive rate (64% and 59%, respectively). Detergent concentrations of 0.05%, 0.15% and 0.3% added to the wool alcohols (10% pet) product resulted in positive reactions in 50%, 50% and 55% of those patients, respectively, and indicated a nonsignificant effect of detergent. In addition, Clark and colleagues summarized eight different series of patch tests with reduced-alcohol-content lanolin. No sources were cited, and specific information about previous lanolin sensitivity and exact concentrations of lanolin alcohol were not reported. However, they stated that among 149 subjects tested with reduced-alcohol-content lanolin in four different clinics, there was “an overall reduction in incidence (of positive reactions) of 99.3%.” They suggested that if pharmaceutical companies limited the free alcohol content of lanolin in topical medicaments to 3% or less, the number of patients sensitized to lanolin would be greatly reduced.
Medical-grade lanolins are thought to be much less antigenic than less purified forms of lanolin. Medilan (Croda, Yorkshire, UK) is a medical grade of highly purified lanolin. It is made through a process of extraction and distillation, which removes all detergents and reduces free alcohols to less than 3%. The pesticide residue in Medilan is less than 1 mg/kg. Morris and colleagues tested 27 AL-101–sensitive patients with Medilan; only one (3.7%) reacted. In 2002, Ardern-Jones and colleagues conducted a three-part study to evaluate allergic contact dermatitis from four types of Medilan. The first group consisted of 61 patients, including 24 atopic individuals and 12 patients with varicose eczema or leg ulcers. The second group consisted of 50 patients with chronic leg ulcers, and the third group consisted of 6 patients who had been previously classified as lanolin sensitive (positive patch–test reactions to 30% wool alcohols). No patient in any of the groups showed a reaction to the four Medilan preparations.
Dermatitis. 2008;19(2):63-72. © 2008 American Contact Dermatitis Society
Cite this: Lanolin Allergy: History, Epidemiology, Responsible Allergens, and Management - Medscape - Apr 01, 2008.