Why do hives appear specifically at night?

Urticaria, also known as hives or nettle rash, primarily manifests as intense skin itching, followed by the appearance of raised, red welts—some pale, some skin-colored, and others reddish—with varying shapes and sizes. Some lesions may persist for extended periods before gradually subsiding, significantly interfering with daily life. So why does urticaria often flare up at night?

Why Urticaria Flares Up at Night

Nighttime urticaria is commonly triggered by temperature changes, external environmental factors, and fluctuations in endocrine hormones. Following an outbreak, affected individuals typically develop skin manifestations such as erythematous patches, rashes, wheals, and pruritus. During skin care, scratching should be avoided to prevent skin injury, secondary infection, or inflammation. Compared with daytime, ambient temperatures are generally lower at night. Individuals with cold-induced urticaria are especially prone to nighttime flares; thus, patients with cold urticaria must take precautions to stay warm after dusk or when ambient temperatures drop, to help prevent symptom onset. During the day, due to work, physical activity, or study, people tend to pay less attention to subtle changes in their skin. Consequently, symptoms such as urticaria or pruritus may go relatively unnoticed. However, once the body relaxes at night, these discomforts become markedly more apparent.

Compared with daytime, the body’s immune response and hormonal secretion are comparatively reduced at night, resulting in diminished cutaneous stress resilience—making urticarial symptoms particularly prominent during nighttime hours. For individuals prone to nocturnal urticaria, it is advisable to avoid consuming allergenic foods such as seafood and crab at night, and to steer clear of “heat-inducing” foods like leeks and toon sprouts, which may exacerbate pruritus and increase overall discomfort. If a mild episode occurs at night, home observation and proper skin care are usually sufficient. For instance, scratching should be minimized; if pruritus is severe, applying a cool, damp towel may provide symptomatic relief.

It is recommended to avoid overeating or binge eating, and to eliminate highly stimulating or allergenic foods—including stale or spoiled ingredients—as well as substances such as pepper, coffee, strong tea, and chili peppers. We hope this information proves helpful to you.