Erythem

Erythem, also spelled erythema in some contexts, is a visible reddening of the skin or mucous membranes resulting from dilation of superficial blood vessels and increased blood flow. It is a sign rather than a disease and can accompany a wide range of conditions, from benign reactions to more serious illnesses. The redness typically blanches with pressure due to the vascular component of the response.

Causes and patterns: Erythema can be transient and harmless (for example, sun exposure or physical exertion) or part of a pathologic process. Common triggers include ultraviolet radiation, heat, skin irritation, infections (viral or bacterial), medications and drug reactions, allergic responses, and systemic inflammatory or autoimmune diseases. Patterns vary from diffuse or localized patches to reticular or punctate arrangements. Some erythemas are named for specific conditions, such as erythema infectiosum (Parvovirus B19), erythema migrans (early Lyme disease), and erythema multiforme (often related to infections or drugs). Erythema marginatum is associated with rheumatic fever.

Diagnosis and management: Diagnosis is primarily clinical, based on the appearance, distribution, and history. Additional tests are guided by the suspected underlying cause. Management focuses on treating the trigger when possible, protecting the skin, and providing symptomatic relief. This may include topical therapies for irritation, sun protection, or systemic treatment for infections or autoimmune disorders.

Prognosis: Erythema is commonly reversible and resolves as the underlying cause is addressed. Persistent redness or new symptoms warrant medical evaluation to exclude chronic or severe conditions.

Etymology: The term derives from Greek erythros for red; in some languages, erythem is used as an alternative spelling.