After contact with grass pollen, seasonal exacerbations of eczematous skin lesions have been described in a subgroup of patients with atopic eczema (AE). Epicutaneous patch testing with aeroallergens (atopy patch test. APT) has been used to investigate these patients. We performed comparative APT in 79 patients with AE and 20 control subjects (14 non-atopic volunteers and six patients with grass pollen allergic rhinoconjunctivitis). Subjects were tested with grass pollen allergen extract in petrolatum and with unprocessed native dry pollen of Dactylis glomerata. Results after 48 h were compared with the patient's history, corresponding skin prick test and specific IgE. Fifteen of the 79 AE patients showed clear-cut eczematous reactions to unprocessed D. glomerata pollen; 14 of these had an elevated serum IgE to D. glomerata and 13 had a positive skin prick test. Twenty patients had a positive APT reaction to grass pollen allergen extract, including 12 of the D. glomerata reactive subjects (P < 0.001). Positive patch test reactions to D. glomerata were seen in 66.7% of cases with and 10.5% of patients without a predictive history of exacerbations during the pollen season. For the standardized extract, these percentages were 75% vs. 16.4% (P < 0.001). No side-effects were observed. Control subjects showed no positive reactions. We conclude that grass pollen preparations may be used to investigate trigger factors for eczematous skin lesions in a subgroup of patients with AE.