Microbial colonization and atopic dermatitis

Purpose of review Atopic dermatitis is a chronic relapsing, pruritic inflammation of the skin, affecting 10-20% of children and 1-3% adults worldwide, with increasing prevalence in highly industrialized countries. Here we review relevant studies, published since June 2002, about immunological triggers in atopic dermatitis, with emphasis on the role of microbial colonization. Recent findings During the past 2 years there has been considerable interest in the mechanisms and trigger factors underlying the increased microbial colonization of atopic skin. Staphylococcus aureus appears to play a significant role as it leads to a worsening of disease severity by producing superantigens that induce a strong proliferation of T cells and favour a T helper type 2-like cytokine profile. In addition, different Malassezia species seem to elicit and maintain skin inflammation after sensitization, but the precise immunological pathway has not yet been described. All these microorganisms are not only perceived as aetiological factors but also as agents responsible either for sustained disease activity or resistance to therapy by modulation of the immune response. Summary New insights into the important role of microorganisms and their key immunomodulatory pathways in atopic dermatitis may have important implications from a therapeutic point of view because patients with atopic dermatitis may benefit from more than just anti-inflammatory treatment in the future.