The significance of previous contact dermatitis for elicitation of contact allergy to nickel.

In 2 earlier studies, we found increased nickel re-test reactivity at earlier experimentally induced nickel eczema sites. The aim of this study was to investigate if earlier contact dermatitis caused by another allergen or earlier irritant contact dermatitis also influenced the reactivity when nickel was applied topically on earlier but healed dermatitis sites. Twenty-three females with contact allergy to both nickel and cobalt were involved in the study. Experimental contact dermatitis from nickel, cobalt and SLS was induced on the lower back. One month later, challenge patch testing with a serial dilution of nickel on the previous but healed dermatitis sites, and on a control area, was done. The tests were read blindly. Significantly higher test reactivity was found at the site with previous allergic contact dermatitis from nickel, and significantly lower test reactivity was observed at the previous SLS dermatitis site.