THE SIGNIFICANCE OF PREVIOUS ALLERGIC CONTACT-DERMATITIS FOR ELICITATION OF DELAYED-HYPERSENSITIVITY TO NICKEL

Several factors, such as amount of allergen, vehicle, anatomic site, i mmunologic status and previous eczema, may influence delayed hypersens itivity reactions. In an extended model, we have studied the significa nce of previous allergic contact dermatitis for elicitation of delayed hypersensitivity to nickel in 25 nickel-allergic females. On 3 occasi ons, 8, 4 and I months before the final challenge patch testing, an ex perimental allergic contact dermatitis from nickel was induced on the lower back. At the challenge patch tl:sting, 4 identical dilution seri es of nickel were tested on 4 areas on the lower back 3 with previous but healed dermatitis and 1 control area. The tests were read in a bli nd way. A significantly higher test :reactivity was found at the areas with a previous allergic contact dermatitis, the shorter the time int erval between the previous provocation and the challenge, the stronger the reaction. These results may be of importance for the understandin g of factors contributing to chronicity of allergic contact dermatitis .