Do antihistamines have a role in asthma therapy?

The coexistence of allergic rhinitis with asthma is widely recognized by clinicians. Histamine, a common mediator for both diseases, has a substantial role in the pathophysiology of asthma through its ability to produce smooth muscle contraction and promote vascular permeability. Because antihistamines often are administered to manage allergic rhinitis symptoms, the effects of antihistamines in asthma should be evaluated. The usefulness of first-generation antihistamines is limited by their side-effect profile, namely sedation and cognitive impairment. Second-generation antihistamines have only a modest effect in attenuating bronchospasm induced by histamine, cold air, exercise, and allergen bronchoprovocation, suggesting that second-generation antihistamines do not have a direct role as a single agent for treating asthma. Studies have shown that controlling allergic rhinitis with antihistamines has a small, indirect effect in improving asthma symptoms. Future work should be directed at improving the potency of antihistamines and defining their antiinflammatory activity.