Are antihistamines useful in managing asthma?

There continues to be a great deal of interest in the anti-asthmatic role of antihistamines. Antihistamines have recently been shown to have anti-inflammatory properties that are more extensive than simply the blocking of histamine receptors. For example, new evidence suggests that the suppression of cell adhesion molecule expression occurs with these drugs. The anti-inflammatory and anti-asthmatic effects of antihistamines have been evaluated in patients with both allergic asthma and rhinitis, given the established association between allergic inflammation of the upper and lower airways, with evidence to suggest that antihistamines have clinically relevant anti-asthmatic properties. As well as conferring benefits in asthma symptom control and the measurement of lung function, studies assessing the effect of histamine receptor antagonists on bronchial hyperresponsiveness suggest that there is bronchoprotection during both methacholine and mannitol challenges. Recently, there has also been considerable interest in the effect of combining an antihistamine with a leukotriene receptor antagonist. This combination has an anti-asthmatic effect that is greater than that of either drug given alone and may be comparable to inhaled corticosteroid therapy.