title: The loss of contact sensitization in man.
abstract: Little is yet known about the duration of contact sensitivity, but frequent exposure of a target to allergen seems to reduce skin reactivity. The aim of this study was to study the persistence of a specific contact sensitivity in 66 patients with alopecia areata, previously sensitized to DNCB (31 patients) and SADBE (35 patients) between 1978-1985. Patch tests were performed with 0.020 ml of different concentrations of DNCB or SADBE in acetone (0.05%, 0.10%, 0.20%, 1%). The results were read in a standardized manner. Of 66 patients, 47 (71%) had positive reactions and 19 (29%) negative. 8 of the 19 negative patients had been treated with DNCB, 11 with SADBE. Approximately 1/3 of the patients previously sensitized had lost their original sensitivity, and this did not seem to be time-dependent. This phenomenon seemed to be clinically correlated because the majority of the patients were from the "low responders" group. We think that acquired unresponsiveness to topical antigen in man is a possible phenomenon, but that it occurs more rarely than in mice and guinea pigs.
authors.affiliation: Department of Dermatology, Ospedali Riuniti di Bergamo, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Valsecchi
authors.forename: A
authors.initials: A
authors.lastname: Rossi
authors.forename: A
authors.initials: A
authors.lastname: Bigardi
authors.forename: P D
authors.initials: PD
authors.lastname: Pigatto
mesh_terms: D000287:Administration, Topical; D000293:Adolescent; D000328:Adult; D000368:Aged; D000506:Alopecia Areata / Q000276:immunology; D002648:Child; D003503:Cyclobutanes / Q000009:adverse effects; D003877:Dermatitis, Contact / Q000209:etiology / Q000276:immunology*; D004137:Dinitrochlorobenzene / Q000009:adverse effects; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010328:Patch Tests
chemical_list: D003503:Cyclobutanes; D004137:Dinitrochlorobenzene; C020637:squaric acid dibutyl ester