Phototherapy (NB-UVB)

Ultraviolet light affects the immune cells and inflammation in the skin, slowing the rapid skin cell turnover of psoriasis, reducing the inflammation of eczema and encouraging pigment cells to return in vitiligo. Phototherapy delivers this light in measured doses from medical lamps, so the benefit is gained with far more control than natural sunlight allows. Narrowband UVB uses a very narrow band of UVB light, around 311 nanometres, and is given in a cabinet lined with tubes, in which you stand for the treatment. PUVA combines psoralen, a medicine that makes the skin more sensitive to light, taken as a tablet or applied by soaking the hands, feet or whole body, with UVA light. Excimer light and excimer laser deliver a concentrated beam of UVB, around 308 nanometres, to individual patches, which suits vitiligo, scalp psoriasis or small resistant plaques. UVA1 is used in some centres for conditions such as localised scleroderma. Home phototherapy units, supervised by a dermatology team, exist for some patients.

Phototherapy is recommended when a skin condition is too widespread or persistent for creams alone, or when a person prefers to avoid or delay tablets, injections or biologic medicines. Psoriasis covering a large area, especially plaque and guttate psoriasis, often responds well. Vitiligo is treated with narrowband UVB for widespread patches and with excimer light for limited areas; the face and neck usually respond better than the hands and feet. Moderate to severe atopic eczema in adults and children can improve, as can early stages of mycosis fungoides, a lymphoma that starts in the skin. Other uses include chronic itch, including itch from kidney or liver disease, lichen planus, some forms of hives, and a short desensitising course in spring for people with polymorphic light eruption, a rash triggered by sunlight. Phototherapy is not suitable for everyone; it is avoided in people with conditions that make the skin abnormally sensitive to light and used with caution after previous skin cancer.

At the first visit your skin type is assessed, and sometimes a small test patch is exposed to find the lowest dose that turns the skin pink. Treatment begins with a low dose that is increased step by step at each session according to how the skin reacts. For narrowband UVB you undress to the extent agreed, wear protective goggles, men protect the genitals, and areas such as the face may be covered if they are not affected. You stand in the cabinet for a period that starts at seconds and builds to a few minutes. For PUVA you take the psoralen tablet about one to two hours before the light, or soak in a psoralen solution beforehand, and you wear UV-protective glasses for the rest of the day after the tablets. Excimer treatment is aimed at each patch with a handpiece and takes a few minutes. Sessions are usually given two or three times a week, never on consecutive days for PUVA. Before each session the nurse asks about burning and any new medicines.

Candidates have a confirmed diagnosis that is known to respond to phototherapy and can attend regularly. Before starting, the team reviews your skin type, history of sunburn and skin cancer, and medical conditions such as lupus, which can be worsened by light, or rare inherited conditions that make the skin extremely sensitive; these may rule treatment out. Medicines that increase light sensitivity, including some antibiotics, diuretics and heart medicines, are checked. PUVA with tablets is generally avoided in pregnancy, in children and in people with significant liver disease or cataracts, while narrowband UVB can be used in pregnancy and in children who can stand still in the cabinet. A skin examination is done to record moles and any suspicious spots. Avoid sunbathing during the course, and bring a list of all medicines and creams. International patients should send previous treatment records, especially the number of past phototherapy sessions, so that lifetime exposure can be taken into account.

There is no recovery in the usual sense; you return to normal activities straight after each session. Moisturising the skin helps, and you should protect treated skin from strong sunlight, as natural sun on top of treatment increases the risk of burning. The practical challenge is the length of the course. A course of narrowband UVB for psoriasis needs about 20 to 30 sessions over about 8 to 12 weeks, and vitiligo often needs months, so a stay of one to two weeks abroad can confirm the diagnosis, set the plan, identify your starting dose and give the first sessions, but it will not complete the treatment. Before travelling, find a phototherapy unit near home that can continue, or ask whether a supervised home unit is an option. Carry a written record of your skin type, the lamp type, each dose given and the plan for increasing it, so treatment can continue without starting again from a low dose.

Phototherapy is a well-established treatment with a long safety record when given by trained staff. The most common side effect is redness, like mild sunburn, which appears several hours after a session and is managed by adjusting or pausing doses. Dryness and itch are common, and some people develop cold sores or a temporary rash. PUVA tablets can cause nausea, and the eyes must be protected from UV for the rest of the day to avoid damage. In the long term, ultraviolet exposure ages the skin and raises the risk of skin cancer; this risk is clearly higher with PUVA than with narrowband UVB, which is why the total number of sessions is recorded over a lifetime and the skin is checked regularly. Psoriasis and eczema often clear or improve substantially after a course, though the effect lasts for months rather than permanently. Vitiligo responds more slowly, and repigmentation varies between body areas and between people.