UVA1 Is Often A1!

Summary and Comment |
April 27, 2012

UVA1 Is Often A1!

  1. Mark V. Dahl, MD

After reviewing the evidence, a workshop group discusses the effectiveness, safety, and costs of UVA1 phototherapy.

  1. Mark V. Dahl, MD

Long-wavelength ultraviolet A light (UVA1, 340–400 nm) has been used to treat skin disease for more than 30 years. UVA1 penetrates deeper than other ultraviolet phototherapies and has different biologic effects than UVB and shorter-wavelength UVA (UVA2, 315–340 nm). UVA1 works via oxygen-dependent mechanisms after photosensitization of endogenous lipids and proteins. DNA dimers are not formed. Dermatologists, physicists, and scientists with experience or interest in UVA1 conducted a workshop review of UVA treatment, grading evidence by the Scottish Intercollegiate Guidelines (SIGN) system.

The group concluded that medium- or high-dose UVA1 works well for morphea. Appearance might worsen, but function (e.g., joint movement) improves. Other conditions with high-level evidence of efficacy were urticaria pigmentosa, atopic dermatitis, dyshydrotic dermatitis, subacute prurigo, and systemic lupus erythematosus (SLE). In SLE, UVA1 seems to benefit both systemic and skin disease. In urticaria pigmentosa, mast cell numbers decrease with treatment. In sclerotic graft-versus-host disease, nephrogenic systemic sclerosis, hypereosinophilic syndromes, lichen sclerosis, scleredema, chronic urticaria, granuloma annulare, sarcoid, psoriasis, and pityriasis lichenoides, UVA1 appears to work well, based mostly on evidence from case series, case reviews, or case reports, so the level of evidence is lower. They also found that UVA1 may be as effective as PUVA (psoralen ultraviolet A) for cutaneous T-cell lymphomas, that benefits may be temporary in granuloma annulare, and that other treatments were more practical in some diseases, such as psoriasis. The most common adverse effect was hyperpigmentation. Patients were often red after treatment due to vasodilatation, and pigmentation in morphea was heightened. Phototoxicity, reactivation of herpes simplex virus, and cholinergic urticaria were less common. Treatment is contraindicated for recipients of UVA-dependent phototoxic drugs. The relative risk for induction of cutaneous malignancies is unknown.


The longer the ultraviolet wavelength, the less energy it delivers to skin and the greater the penetration of photons. UVA1 is suited for conditions affecting the dermis, such as sclerosis. To achieve enough energy, treatment units use metal halide tubes, require lots of electricity, and generate enough heat to require special ventilation. Although UVA1 is present in sunlight and other UVA-producing light sources, therapeutic success requires use of these high-output units.


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