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Introduction: Epicutaneous (e.c.) allergen exposure is an important route of sensitization toward allergic diseases in the atopic march. Allergen sources such as house dust mites contain proteases that involve in the pathogenesis of allergy. Prostanoids produced via pathways downstream of cyclooxygenases (COXs) regulate immune responses. Here, we demonstrate effects of COX inhibition with nonsteroidal anti-inflammatory drugs (NSAIDs) on e.c. sensitization to protease allergen and subsequent airway inflammation in mice. Methods: Mice were treated with NSAIDs during e.c. sensitization to a model protease allergen, papain, and/or subsequent intranasal challenge with low-dose papain. Serum antibodies, cytokine production in antigen-restimulated skin or bronchial draining lymph node (DLN) cells, and airway inflammation were analyzed. Results: In e.c. sensitization, treatment with a nonspecific COX inhibitor, indomethacin, promoted serum total and papain-specific IgE response and Th2 and Th17 cytokine production in skin DLN cells. After intranasal challenge, treatment with indomethacin promoted allergic airway inflammation and Th2 and Th17 cytokine production in bronchial DLN cells, which depended modestly or largely on COX inhibition during e.c. sensitization or intranasal challenge, respectively. Co-treatment with COX-1-selective and COX-2-selective inhibitors promoted the skin and bronchial DLN cell Th cytokine responses and airway inflammation more efficiently than treatment with either selective inhibitor. Conclusion: The results suggest that the overall effects of COX downstream prostanoids are suppressive for development and expansion of not only Th2 but also, unexpectedly, Th17 upon exposure to protease allergens via skin or airways and allergic airway inflammation.