`Irritants' Increase the Response to an Allergen in Allergic Contact Dermatitis

TLDR

The study examined how irritants affect allergen‑induced reactions in 15 patients. Allergen dilutions were applied to patches, removed after 24 h, then irritants were added for 24 h to one set, with controls, and reactions were quantified at 72 h. Combined allergen and irritant exposure produced a stronger reaction than either alone, converting subthreshold allergen doses into positive responses and suggesting irritants amplify allergic contact dermatitis, potentially explaining dermatitis in patients with negative patch tests.

Abstract

We studied the effect of "irritants" on the response to an allergen in 15 patients. Dilutions of allergens were applied in duplicate, and 24 hours later they were removed and sodium lauryl sulfate (11 subjects) or anthralin (dithranol) (four subjects) was applied for a further 24 hours to one set of patches. Control dilutions of irritants alone were applied. Responses were measured objectively at 72 hours. The response to both allergen and irritant was greater than to either alone. Doses of allergen, which did not produce a response when applied alone, produced a response when an irritant was added. Irritants therefore increase the allergic contact dermatitis response and may explain the presence of contact dermatitis in patients with negative patch tests.