Histamine Modulates Sweating and Affects Clinical Manifestations of Atopic Dermatitis.

Many factors such as food or environmental allergens, bacteria, fungi, and mental stress aggravate the condition of atopic dermatitis (AD) eczema. Sweating can also exacerbate AD, and patients are aware of that. In the past, it has been reported that contamination of skin surface antigens by sweat induces acute allergic reactions and that sweating functions of AD patients via axonal reflexes are decreased. Histamine demonstrably inhibits acetylcholine-induced sweating in both mice and humans via histamine H1 receptor-mediated signaling. In sweat glands, acetylcholine inactivates glycogen synthase kinase 3β (GSK3β), a kinase involved in endocytosis and secretion, whereas simultaneous stimulation with histamine activates GSK3β and inhibits sweat secretion. Thus, histamine might be involved in the mechanism of abnormal skin dryness in patients with AD via decreasing sweat secretion. On another front, some patients secrete sweat normally. Patients with regular sweating are prone to develop skin disorders such as papules or erythema by residual sweat left on the skin surface. Patients with decreased sweating are prone to develop disorders characterized by xerosis, lichenoid changes, prurigo by elevated skin temperature, skin dryness, and compromised skin conditions. Careful inspection of skin manifestations provides a good indication of a patient's ability to sweat.