The present invention relates to the use of an arginase inhibitor for the preparation of a medicament for the prophylactic maintenance therapy of an asthmatic or allergic patient by preventing obstruction of upper and lower airways, in particular allergen-induced bronchial obstruction and/or airway hyperresponsiveness. The patients are either asthmatic or have allergic rhinitis. Preferably, the arginase inhibitor is 2(S)-amino-6-boronohexanoic acid (ABH).
