Patch test reactions to inhalant allergens in atopic dermatitis

To study whether inhalant allergens could induce eczematous reactions on normal skin of atopic patients we applied birch pollen and house dust mite antigens at 500 times the concentration used for prick testing as epicutaneous tests. Six out of 17 patients with atopic dermatitis in remission had positive delayed type reactions to birch pollen and three to house dust mite. Only one out of 13 atopic patients without history of atopic dermatitis but with seasonal allergic rhinitis had a positive patch test reaction to birch pollen and no patient had positive test reactions to house dust mite. No positive patch test reactions to birch pollen or house dust mite were seen in the ten healthy control subjects. In patients with positive test reactions biopsies from the test sites revealed epidermal spongiosis and vesiculation. Immunostaining of the epidermis revealed keratinocytes displaying both CD1 and HLA-DR. The present study suggests that inhalant allergens can exacerbate atopic dermatitis.