UVA1

UVA1 refers to a range of long-wave ultraviolet A radiation used in dermatologic phototherapy. It encompasses wavelengths roughly 340 to 400 nanometers, with many sources emphasizing 340–360 or 360–380 nm as the most active portion. UVA1 phototherapy uses specialized light sources to deliver this radiation without the photosensitizing agent psoralen (unlike PUVA therapy).

Treatment is administered in a clinical setting, typically two to five sessions per week over several weeks. Doses are titrated to the patient’s skin type and tolerance and are usually measured in joules per square centimeter per session. Treatment duration per session varies but commonly lasts 20 to 40 minutes.

Mechanism: The longer wavelengths penetrate deeply into the dermis, affecting resident immune cells and fibroblasts. UVA1 can induce apoptosis of dermal T cells, modulate cytokine signaling, and stimulate remodeling of collagen and elastin, contributing to anti-inflammatory and antifibrotic effects.

Indications and efficacy: Strong evidence supports use for adult atopic dermatitis and localized scleroderma (morphea). Some data exist for other inflammatory dermatoses and selected cases of cutaneous T-cell lymphomas, but results are more variable. UVA1 is often chosen when deeper dermal involvement is present and safer alternatives are limited.

Safety and considerations: Common short-term side effects include erythema, warmth, and dry or itchy skin. Long-term risks include photoaging and potential cumulative skin damage; the cancer risk is not fully established but is considered lower than UVB for skin cancer in many settings. Protective eye shielding is required; care is taken in photosensitive individuals, pregnant patients, and those with a history of melanoma or other photosensitivities.