Anhidrosis: An underappreciated factor in dermatologic diseases.

Dissipation of body heat, essential to human life, is largely achieved through sweating. If sweating does not occur normally-as in patients with hypohidrosis (reduced sweating) or anhidrosis (lack of sweating)-the ability to dissipate heat via evaporative mechanisms is overwhelmed. Body temperature may rise, leading to heat-related illness, including heat intolerance, hyperthermia, heat exhaustion, heat stroke, and even death. In patients seen by a dermatologist, anhidrosis may underly and contribute to their symptoms and signs but may be difficult to detect given a limited availability of tools to measure anhidrosis. An association between anhidrosis and skin symptoms including flushing syndromes (eg, facial flushing and erythromelalgia) and widespread skin symptoms (eg, itching, burning, numbness, or tingling, and paresthesias) has recently been described. This review explores the existing dermatologic literature on anhidrosis including clues to the pathophysiology of these disorders, its relationship to skin diseases and symptoms, the tests currently available, and approaches to management. Recognition of an underlying anhidrosis by dermatologists may be important for providing optimal management for patients with heat-related symptoms.