Ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

light therapy or ultraviolet phototherapy is a treatment for

psoriasis Psoriasis is a long-lasting, noncontagious autoimmune disease characterized by patches of abnormal skin. These areas are red, pink, or purple, dry, itchy, and scaly. Psoriasis varies in severity from small localized patches to complete b ...

vitiligo Vitiligo (, ) is a chronic autoimmune disorder that causes patches of skin to lose pigment or color. The cause of vitiligo is unknown, but it may be related to immune system changes, genetic factors, stress, or sun exposure, and susceptibili ...

and other skin diseases.

Mechanism of action

Ultraviolet light exerts its therapeutic effects largely by modulating cutaneous immune responses and inducing

apoptosis Apoptosis (from ) is a form of programmed cell death that occurs in multicellular organisms and in some eukaryotic, single-celled microorganisms such as yeast. Biochemistry, Biochemical events lead to characteristic cell changes (Morphology (biol ...

of pathogenic cells, thereby reducing

inflammation Inflammation (from ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin ''calor'', '' ...

in a variety of photoresponsive skin disorders.

Treatment modalities

There are two main treatments: UVB that is the most common, and PUVA. Despite the advent of biologic drugs, narrow-band UVB remains an important option for moderate-to-severe inflammatory dermatoses and was the most cost-effective therapy for

in a 2023 analysis.

UVB phototherapy

There are four UVB types of lamps: Fluorescent Broad-Band UVB that emit 280–330 nanometres, Fluorescent Narrow-Band that emit 312 nanometres, Excimer that emit 308 nanometres and LED that emit 290–300 nanometres.

PUVA phototherapy

PUVA PUVA (psoralen and UVA) is an ultraviolet light therapy treatment for skin diseases: vitiligo, eczema, psoriasis, graft-versus-host disease, mycosis fungoides, large plaque parapsoriasis, and cutaneous T-cell lymphoma, using the sensitizing e ...

means UVA +

psoralen Psoralen (also called psoralene) is the parent compound in a family of naturally occurring organic compounds known as the linear furanocoumarins. It is structurally related to coumarin by the addition of a fused furan ring, and may be considered a ...

. It consists of irradiation of the skin with the UVA

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

light, from a

fluorescent Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with color ...

bulb or LED lamps. Clinical protocols sometimes augment PUVA with interferon-α, a strategy that can improve complete-response rates while allowing lower cumulative UVA doses.Beigi, P. K. M. (2017). Treatment (Chap. 6). In ''Clinician’s Guide to Mycosis Fungoides'' (pp. 23–34). Springer. https://doi.org/10.1007/978-3-319-47907-1_6 PUVA therapy delivers deeper-penetrating UVA after oral administration of 8-methoxypsoralen, and is therefore often selected for thicker or more recalcitrant plaques, whereas narrow-band UVB (311–312 nm) is preferred for superficial lesions because of its shallow penetration.

Equipment and usage

Tanning beds are used both in dermatology practices for the treatment of cosmetic skin conditions (such as psoriasis, acne, eczema and vitiligo) and in indoor tanning salons for cosmetic tanning. Typical treatment regimens involve short exposure to UVB rays 3 to 5 times a week at a hospital or clinic, and repeated sessions may be required before results are noticeable. Almost all of the conditions that respond to UVB light are chronic problems, so continuous treatment is required to keep those problems in check. Home UVB systems are common solutions for those whose conditions respond to treatment. Home systems permit patients to treat themselves every other day (the ideal treatment regimen for most) without the frequent, costly trips to the office/clinic and back, mainly when the area is small, and the price of the lamp is low.

Safety and side effects

A 2024 multi-centre study reported higher incidences of

squamous cell carcinoma Squamous-cell carcinoma (SCC), also known as epidermoid carcinoma, comprises a number of different types of cancer that begin in squamous cells. These cells form on the surface of the skin, on the lining of hollow organs in the body, and on the ...

basal cell carcinoma Basal-cell carcinoma (BCC), also known as basal-cell cancer, basalioma, or rodent ulcer, is the most common type of skin cancer. It often appears as a painless, raised area of skin, which may be shiny with Telangiectasia, small blood vessels ru ...

and

melanoma Melanoma is the most dangerous type of skin cancer; it develops from the melanin-producing cells known as melanocytes. It typically occurs in the skin, but may rarely occur in the mouth, intestines, or eye (uveal melanoma). In very rare case ...

among patients treated with narrow-band UVB, highlighting the need for long-term dermatological

surveillance Surveillance is the monitoring of behavior, many activities, or information for the purpose of information gathering, influencing, managing, or directing. This can include observation from a distance by means of electronic equipment, such as ...

. Side-effects may include itching and redness of the skin due to UVB exposure, and possibly sunburn, if patients do not minimize exposure to natural UV rays during treatment days. Cataracts can frequently develop if the eyes are not protected from UV light exposure. To date, there is no link between an increase in a patient's risk of skin cancer and the proper use of narrow-band UVB phototherapy. "Proper use" is generally defined as reaching the "Sub-Erythemic Dose" (S.E.D.), the maximum amount of UVB your skin can receive ''without'' burning. Certain fungal growths under the toenail can be treated using a specific wavelength of UV delivered from a high-power LED (light-emitting diode) and can be safer than traditional systemic drugs.{{Citation needed, date=April 2023

References

Dermatologic procedures