H1-Antihistamines: more relevant than ever in the treatment of allergic disorders.

Histamine is an important chemical mediator of inflammation, vasodilation, increased vascular permeability, decreased peripheral resistance, airway smooth muscle contraction, and sensory nerve stimulation causing itching. It also plays a significant role in neurotransmission and in cardiac function. In allergic rhinoconjunctivitis and urticaria, there is strong evidence for the role of H(1)-antihistamine treatment. In asthma, additional dose-response studies, including higher doses of antihistamines than those used in allergic rhinitis, are needed to determine the role of antihistamines. In atopic dermatitis, the itch-relieving topical glucocorticoid-sparing effects of H(1)-antihistamines also require further documentation. The potential benefits of each H(1)-antihistamine should be weighed against the potential risks, and second-generation H(1)-antihistamines with excellent, well-documented safety records should be used in preference to older, less safe H(1)-antihistamines. Second-generation H(1)-antihistamines are more relevant than ever in the treatment of allergic disorders.