The effect of controlled exposure to grass pollen in an environmental challenge chamber on dermal symptoms in patients with atopic dermatitis

It has frequently been speculated that pruritus and skin lesions develop after exposure to aeroallergens in sensitized patients with atopic dermatitis (AD). The aim of the present study was to assess the cutaneous reactions to grass pollen in adult patients suffering from AD with accompanying IgE sensitization to grass allergen, in an environmental challenge chamber in a single centre, double-blind, placebo-controlled study. Subjects were challenged on two consecutive days by exposure to either 4000 pollen grains m -3 of Dactylis glomerata pollen or clean air (placebo). The severity of AD was assessed at each study visit, prior and up to 3 days postchallenge by clinical scores such as objective Scoring Atopic Dermatitis (SCORAD) (primary end point), Investigator Global Assessment (IGA) and 'local SCORAD'. In objective SCORAD, which is a well-defined scoring system for AD, the extent and intensity items are considered, while subjective symptoms are left out. Separate evaluation of air-exposed and textile-covered skin areas was performed by IGA and 'local SCORAD'. By 'local SCORAD' the intensity of an air-exposed and a covered target lesion that had been defined prior to exposition was assessed. In addition, serum CCL17 (thymus and activation-regulated chemokine; TARC) levels were determined by enzyme-linked immunosorbent assay. Exposure to grass pollen induced a significantly higher increase of objective SCORAD from prechallenge to postchallenge day 3 in the verum group compared with the placebo group. Only in the verum group could a significant worsening of air-exposed areas vs. textile-covered skin be observed. With exposure to grass pollen a trend of increased CCL17 could be observed. This pilot study demonstrates that controlled exposure to airborne allergens of patients with an 'extrinsic' IgE-mediated form of AD (as demonstrated by the presence of IgE for D. glomerata) induced a worsening of dermal symptoms. This proof of concept implies the need for allergen avoidance as a preventive measure in these patients. Aerogen challenges with airborne allergens might be a useful model to investigate novel drugs in AD.