Allergens in Lanolin
Researchers have been investigating antigenic compounds in lanolin for more than 50 years. Although no specific antigens have been determined, most researchers agree that any such allergen (or allergens) resides in the alcoholic fraction produced by the hydrolysis of lanolin.[6,48,49] Sulzberger and Lazar were the first to report this in 1950. In their study, four patients with previous allergic reactions to lanolin were tested with 12 different lanolin-related substances, including lanolin fatty acids, mixed lanolin alcohols, two types of lanosterol, two types of cholesterol, and three different commercial brands of lanolin. The fractions containing the mixed lanolin alcohols were the only substances that elicited a reaction in all subjects.[50] Three years later, Sulzberger and colleagues tested 19 lanolin-sensitive patients to one or more of 16 different lanolin products, including cholesterol, mixed lanolin alcohols, aliphatic alcohol fraction, cetyl alcohol, mixed lanolin fatty acids, and combined lanolin fatty acids and alcohols. Of the substances tested, the fraction containing the combination of lanolin alcohols and lanolin fatty acids elicited a positive reaction in 18 (94.7%) of 19 individuals tested. Mixed lanolin alcohols (5% in olive oil) produced a response in 16 (84.2%) of 19 patients, and reactions to the aliphatic alcohol fraction (5% in olive oil) were positive in 14 (77.7%) of 18 subjects. The fatty acids (5% in olive oil) caused positive patch–test results in only 15.7% of the subjects, and other substances tested showed similarly low rates.[26]
More evidence pointing toward the alcoholic fraction of lanolin as the sensitizing agent came in 1968 from De Beukelaar, who tested three patients with suspected reactions to Eucerit, which contains wool fat-alcohol fractions and petrolatum. When water is added to this mixture, the resulting commercial product is known as Aquaphor (Beiersdorf). These patients were patch-tested with cholesterol, ional (not further characterized), and wool fat-alcohol fractions A and B, in addition to Eucerit. The common elicitor in all patients was fraction B of the wool fat-alcohols. One patient had positive reactions to Eucerit, both wool fat-alcohol fractions, and cholesterol, which led the author to postulate that the culprit may lie within cholesterol, an oxidation product of cholesterol, or possibly one of those products reacting with the alcohol fraction.[51] Ellis was the first to propose the idea that cholesterol in lanolin may be the cause of contact dermatitis from lanolin, 21 years before De Beukelaar made this claim.[52]
Other studies have indicated that a mixture of sterols may be more important than different fractions of lanolin alcohols. In a report by Oleffe and colleagues in 1978, of 30 subjects tested, 23 reacted to mixed sterols while only 16 and 14 showed positive reactions to mixtures A and B of lanolin alcohols, respectively.[53] All were criticized by Kligman for the unlikelihood that cholesterol or any mixture of sterols could cause lanolin allergy.[2] In a guinea pig maximization test, two sterol-like fractions were unable to induce sensitization whereas the methylated alcohol fraction of lanolin was able to sensitize 10 to 30% of 10 animals.[54]
The fatty acid fraction of lanolin has also been implicated as a sensitizer, by Sulzberger and colleagues. In their previously mentioned study, they were successful in eliciting positive patch-test results in 2 of 19 patients who had been previously regarded as “lanolin sensitive.” This rate, however, is much lower than the rates found for alcoholic fractions.[26]
Pesticide residues in lanolin may result from either “dipping” sheep in various pesticides to control external parasites or from ingestion of grass containing pesticides.[55,56] In the late 1980s, several published reports implicated these residues as a source of sensitization.[57–59] However, a comprehensive literature search did not yield any studies specifically evaluating the allergenic potential of pesticides in lanolin.
Hypersensitivity to hydrogenated lanolin was first described by Vollum in 1969.[60] Sugai and Higashi became interested in hydrogenated lanolin after dermatitis from an ointment containing hydrogenated lanolin increased in Japan in the early 1970s. It was originally suspected that hydrogenated lanolin would be less sensitizing than hydrous lanolin. However, their study found that among dermatitis patients, 38 (5%) of 756 reacted to hydrogenated lanolins whereas only 2.8% (21 of 756) reacted to anhydrous lanolin. It is possible that the products of hydrogenation were allergenic or that contamination with other allergens (such as nickel, copper, and chromium) during the hydrogenation process could have affected reactivity.[61]
It is well established that some samples of lanolin and its derivatives may produce a positive reaction whereas others will not.[28,62,63] In Denmark, Hjorth and Trolle-Lassen tested “fresh” and “old” (ie, stored in a tight jar for 7 years) Eucerin (not further specified) in 20 lanolin-sensitive patients; 11 of the 20 patients reacted positively to fresh lanolin whereas all reacted to old lanolin, suggesting that oxidation products may be antigenic.[28] This provides some evidence for oxidation products as antigens; however, larger study populations are needed to further investigate the relevance of these reactions.
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.
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