Allergic Contact Dermatitis: A Historical View of its Mechanism

Abstract

The highlights of the history of the search for the mechanism underlying allergic contact dermatitis are presented. Although the concept and the clinical features of contact allergy had become well-established around the turn of the last century, the mechanism remained largely unknown. The first break, an epochal one in various ways, came in 1942 with the discovery of the role of specifically sensitized lymphocytes; it explained the previous failure to find conventional serum antibodies, for which a search had been made for decades. However, the discovery of the role of lymphocytes did not yet answer the question of whether the skin was merely a target organ, or was in some as yet unknown way a participant in the contact allergic response. This question was answered in 1973 with the discovery of the antigen-presenting role of Langerhans cells. During the past 10 years, major progress has been made with the demonstration of the role of keratinocytes in contact allergy, although this role has not yet been fully explored. With these last two major steps, it has become evident that at least 95% of indigenous epidermal cells participate in the mechanism of this important and clinically fascinating disease.