When the patch test reaction to aeroallergens in atopic dermatitis (AD) patients is considered a representative model to study its pathogenesis, then eosinophils may really be involved in the pathogenesis of AD. They actively infiltrate the dermis and the epidermis after patch testing with aeroallergens and even release part of their granular constituents. The role eosinophils play in the pathogenesis of AD is still open for discussion. The granular components of the eosinophil may certainly contribute to a situation of chronic inflammation. On the other hand one should seriously consider the possibility of a beneficial role also, i.e. modulation of the lymphoproliferative response.