Challenge reactions in atopic dermatitis after percutaneous entry of mite antigen.

We succeeded in reproducing an eczematous lesion on the apparently normal skin of a patient with atopic dermatitis by scratching and continuous application of an ointment containing ferritin-labelled mite antigen. Percutaneous entry of mite antigen was demonstrated in skin biopsies by Fe-staining. Scratched skin first showed an urticarial reaction typical of type I allergy which later changed into an eczematous reaction typical of type IV allergy. This change was also shown histologically.