Antihistamines and steroids in pediatric dermatology

Abstract

Histamine-receptor antagonists, or antihistamines, compete with histamine for receptors in various tissues and are classified into H1and H2-antihistamines. The principal actions of H1-antihistamines are on vasodilatation and increased vascular permeability. They reduce whealing and suppress the wheal-and-flare reaction of the axon reflex in acute urticaria as well as the associated itching. H2-antihistamines are mainly used in peptic ulcer disease, but the presence of H2-receptors in the cutaneous microvasculature has prompted their use in dermatology, too. It seems that an H2-antihistamine given concurrently with an H1-antihistamine may modestly improve itching and wheal formation in some patients with urticaria refractory to treatment with an H1-antihistamine alone, but the available evidence does not justify the routine use of H2-antihistamines in urticaria management. H1-antihistamines are further classified into firstand second-generation agents. First-generation antihistamines include diphenhydramine, chlorpheniramine, and hydroxyzine and may cause sedation due to their property of crossing the blood-brain barrier. Secondgeneration, or low-sedating, H1-antihistamines include terfenadine, astemizole, cetirizine, loratadine, fexofenadine, and mizolastine.