Also referred to as light therapy, phototherapy is a treatment for skin conditions that involves exposing the skin to certain kinds of light on a regular basis, under medical supervision. The treatment can be carried out in a medical setting such as a psoriasis clinic or doctor’s office or it can be performed at home, using a phototherapy unit.
Natural sunlight can prevent or improve symptoms in many inflammatory skin conditions. Ultraviolet (UV) light is the invisible part of sunlight that can be used to help with such conditions. The UV radiation in sunlight is divided into three different bands of rays: ultraviolet light type A(UVA), type B (UVB), and type C (UVC ). UVB is the middle light energy that occurs between UVA tanning rays and the intense UVC rays. UVA is also known as “UV Aging rays,” since these rays can cause sunburn, skin aging, and skin cancer. UVB is also referred to as “UV burning rays,” since these rays cause sunburn and are the most common cause of skin cancer. UVC rays are the strongest of the rays, but are absorbed by the ozone layer and do not reach earth.
Although UVB rays are responsible for causing sunburn, when carefully controlled, they are extremely effective at treating skin conditions such as eczema and psoriasis. In phototherapy, this light is produced by machines and shone onto the whole body or the part of the body that requires treatment.
UVB therapy may be broad band or narrow band. The difference is that narrow band uses a smaller range of UV light, while broad band uses the full UV spectrum. The reduced spectrum of narrow-band UVB therapy means some of the more damaging wavelengths are excluded, which has made this form more popular than broad band. It is also more intensive, so treatment time is usually shorter with narrow band UVB. A number of studies have shown that narrow band UVB clears psoriasis more quickly than broad band UVB and also results in longer remissions.
UVB phototherapy is the preferred treatment choice for people with psoriasis or eczema that has failed to respond to topical treatments. The therapy has been used in clinics and hospitals since it was developed in the 1920s. It improves skin conditions by reducing itch and calming inflammation. It also increases vitamin D production and strengthens bacteria-fighting mechanisms in the skin.
The treatment schedule varies, with skin being exposed to UVB light anything from two to five times a week over the course of 15 to 30 treatments. The exposure time may be less than one minute initially, and then gradually increased until the skin starts to turn slightly pink. The initial dose is chosen, based on the patient’s description of how they usually tan in sunlight or on a test dose of the light that is administered. After a couple of months, a weekly treatment maintenance program is usually advised, since the skin condition can seem to have cleared for months before flaring up again.
The most common side effect is a mild sunburn effect and significant side effects are uncommon. The sunburn is usually most severe around 8 hours after the treatment, after which it fades in the days that follow. Anybody who is treated tans to some degree. Occasionally, white and brown spots appear on the skin after several rounds of therapy or itching may worsen.
If no improvement is seen, the patient may be prescribed medicated creams or treatment with another form of phototherapy called PUVA (psoralen + UVA). For PUVA, UVA radiation is combined with a chemical sensitizer called psoralen to increase the effects of UVA.
Treating skin conditions with UVB at home is a convenient and cost-efficient choice for some people. Again, a consistent treatment schedule must be followed. Patients are initially treated in a clinical setting before they start to use the therapy at home.
Reviewed by Susha Cheriyedath, MSc