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Ann Allergy Asthma Immunol. 1999 Aug;83(2):83-9; quiz 89-93.

Environmental exposure unit: a system to test anti-allergic treatment.

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Queen's University, Kingston General Hospital, Ontario, Canada.



Reading this article will enable readers to recognize the Environmental Exposure Unit (EEU), its historic development and its current role as a system to test anti-allergic treatment; to recognize clinical relevance of this test system and its relationship with other pollen challenge methods of evaluation of anti-allergic medication; and, to recognize variables associated with standard clinical studies of anti-allergic medication. Readers will review four studies of antihistamines tested in the Environmental Exposure Unit, three studies on nasal corticosteroids, one on topical eye drops and one on immunotherapy conducted in the EEU.


The EEU has been in operation since 1985 preceded by a prototype challenge system to assess respiratory effects of urea formaldehyde foam insulation. A number of studies on the onset of action and efficacy of different antihistamines and nasal corticosteroids as well as other treatments have been completed producing accurate and consistent results influenced to some extent by study designs.


Studies of commonly used antihistamines and nasal corticosteroids are discussed in detail and represent several of the studies undertaken to date in the EEU.


Controlled ragweed pollen exposure using the EEU has shown that some antihistamines demonstrate an onset of action within 30 minutes while others have taken up to 3 hours to produce significant effect. Nasal corticosteroids evidenced the onset of clinical improvement at 5 to 6 hours with significance over placebo between 6 and 12 hours depending on dose.


The EEU is an effective pollen delivery system that accurately and consistently determines the onset of action and efficacy of anti-allergic treatment in large groups of subjects. It eliminates variables associated with various other methods of evaluation of these medications but does not supplant the need for such evaluations.

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