•The H2 receptor is found on the parietal cells within the stomach, heart and to a limited extent, in immune cells and vascular smooth muscle. Activation of the H2 receptor stimulates vasodilation and release of the gastric acids required for digestion. Physical responses to the H2 receptor include a decrease in the chemotaxis and activation of neutrophils and basophils, stimulation of suppressor T cells, lymphocyte proliferation and natural killer cell activity. Combined activation of H1 and H2 receptors contributes to rhinorrhea and swelling of the nasal airways.