Controlled exposure to grass pollen in an environmental challenge chamber induces a worsening of cutaneous symptoms in patients with atopic dermatitis

Background: Inhalant allergens may act as a trigger factor of atopic dermatitis (AD). In case reports and interventional studies on bronchial or nasal allergen provocation with inhalant allergens a deterioration of skin symptoms in a subgroup of AD patients has been described. Aside from this atopy patch tests (APT) with inhalant allergens revealed a high diagnostic specificity with regard to the patients' history. However, a diagnostic tool testing the clinical relevance of inhalant sensitization in patients with AD by provocation as near as possible to 'true life' conditions is not available. The aim of this single center, double-blind, placebo-controlled study was to assess the cutaneous reactions to grass pollen in adult patients suffering from AD with accompanying IgE-sensitization to grass pollen allergen. For this purpose, AD patients were exposed to grass pollen in an environmental challenge chamber (ECC). Method: On two consecutive days sensitized patients were challenged with either 4000 pollen grains/m3 of Dactylis glomerata pollen (verum) or clean air (placebo). Prior to the challenge, on each challenge day (Day 1 and 2) and also during a follow-up period (Day 3-5) the severity of AD was assessed by objective SCORAD (primary endpoint). Additionally, air-exposed and textile covered skin areas were separately scored by IGA and 'local SCORAD'. By 'local SCORAD' two representative target lesions - one textile covered and one air-exposed - in each patient were evaluated. As biomarker of the disease activity serum CCL17 levels were determined by ELISA. Results: In patients exposed to grass pollen a significantly higher increase in objective SCORAD from pre-challenge to postchallenge Day 3 in the verum group compared to the placebo group was observable (P = 0.010). Of note, a significant worsening of air-exposed rather than of textile covered skin occurred. A trend towards an increase of CCL17 serum levels in grass pollen exposed patients was obvious. Conclusion: By this proof-of-concept study, effects of an inhalant allergen on cutaneous symptoms in selected AD patients could clearly be demonstrated. Our results support the need for allergen avoidance as a preventive measure in these patients. Aerogen allergen challenge by means of an ECC might represent a useful procedure also for research on therapeutic agents in AD.