Phototherapy is the controlled exposure to sunlight or artificially produced ultraviolet radiation for medical treatment. Measured doses of specific ultraviolet wavelengths are used to treat many skin conditions, including dermatitis, psoriasis and vitiligo. Ultraviolet (UV) light may be used alone or in combination with topical or oral medications.
The ultraviolet spectrum is divided into ultraviolet A (UVA) and ultraviolet B (UVB) light. Topical moisturizers or coal tar preparations may be used to enhance UVB effects. UVA may be used with drugs called psoralens to produce results that ultraviolet light or the medication alone could not accomplish. Psoralens may be administered orally or applied topically through creams, ointments, lotions or a bath water solution.
The doses of ultraviolet light used are often determined by testing skin that is not usually exposed to sunlight (e.g., lower back, buttocks). This allows a dermatologist to evaluate the patient’s individual sensitivity to ultraviolet light. Moisturizers or medications used with phototherapy are usually administered before ultraviolet light exposure.
Ultraviolet light is typically administered in doses that cause the skin to just barely turn red. With repeated exposures, a gradual increase of the dose is required. The rate of increase depends on whether or not psoralens are used, treatment frequency and the outcome of the previous treatment. Phototherapy treatment is generally continued until complete remission is achieved or no further improvements can be obtained. Maintenance sessions may be used to increase remission times.
Although phototherapy can greatly improve or even clear many skin conditions, it poses risks. Short-term risks include burning similar to sunburn that can be very severe. Long-term risks include photoaging of the skin and the formation of skin cancer. Oral psoralens pose further risks, such as the risk of cataract formation (condition in which the lens of the eye becomes cloudy).
It is important to have the skin checked for skin cancer, and other negative conditions that may develop due to phototherapy, for many years after the treatment has ended.
About phototherapy
Phototherapy is the controlled medical exposure to sunlight or artificially produced ultraviolet radiation. Measured doses of specific ultraviolet (UV) wavelengths are used to treat many skin conditions (e.g., pruritus, atopic dermatitis). However, this therapy is not for everyone. It is not typically recommended for children or patients with sun allergies or conditions that worsen when exposed to sunlight.
Phototherapy works by a variety of mechanisms, including:
Reducing DNA synthesis, which reduces accelerated cell growth, such as that caused by cells in the epidermis affected by psoriasis.
Inducing release of certain hormones (prostaglandin) and proteins (cytokines) that cause light reactions (e.g., increased pigmentation, sunburn).
Suppressing the immune system, which reduces the exaggerated immune response of contact allergies and hypersensitivity.
Topical agents and combination therapies are often used in combination with phototherapy. The goal of this is to minimize the risk of long-term side effects, increase the effectiveness of each treatment and reduce the doses of ultraviolet light required.
Conditions treated with phototherapy
Many skin conditions can be treated with phototherapy, including:
Pruritus (itchiness). Phototherapy may be beneficial in many different forms of pruritus, particularly those associated with diabetes, liver disorders, uremic pruritus (itchiness due to kidney problems), and itchiness without an identifiable cause.
Atopic dermatitis. Dermatitis (inflammation of the skin) with intense itching, often due to an allergic reaction. Phototherapy has been used in the treatment of atopic dermatitis for decades. It is most helpful in chronic, moderate cases of the disease and may reduce the need for potent corticosteroids. However, many treatment exposures may be required to control the condition and recurrence rates are high and rapid, requiring frequent maintenance sessions.
Seborrheic dermatitis. Dermatitis marked by oily scales, crusty yellow patches and itching. Phototherapy may be very effective in severe cases of seborrheic dermatitis, but flares may occur, requiring further treatment.
Psoriasis. A skin disease characterized by raised, red patches of skin often covered with silvery scales. Phototherapy is frequently used to help manage many types of psoriasis, although the erythrodermic and pustular varieties may be more difficult to treat. It may be combined with other therapies (e.g., anthralin, vitamin D analogs, retinoids).
Vitiligo. Patches of skin lacking pigmentation (color). Phototherapy may cause repigmentation of the skin by stimulating the production of melanocytes. Doses of ultraviolet light must be tended to more carefully than in other disorders because of increased photosensitivity associated with the condition.
Generalized lichen planus. A skin condition marked by flat, shiny, violet papules. Phototherapy may provide an effective alternative to corticosteroids in the treatment of generalized lichen planus. Complete remissions may occur, although it may require many sessions and not all patients respond.
Alopecia areata. Patches of hair loss. Certain forms of phototherapy (topical or systemic psoralens plus ultraviolet A [PUVA] light) may help to regrow hair. However, the response varies from patient to patient.
Urticaria pigmentosa. A skin disease with brownish papules that sting when touched. Phototherapy may relieve the itching and stinging and may flatten and reduce lesions. In many cases, even long-term symptoms (e.g., migraines, flushing) decrease gradually as treatment is continued. Recurrences are common but respond as well to additional treatment as the original lesions.
Generalized granuloma annulare. A chronic rash marked by flat, ring-like spots with lighter centers. Phototherapy has been reported to clear the lesions completely, although long-term maintenance may be required to prevent recurrences.
Cutaneous graft-versus-host disease (GvHD). A condition in which cells from transplanted tissue of a donor cause an immune system attack on the tissue of the recipient. Phototherapy can improve some types of GvHD. There is some debate as to whether phototherapy may be useful in the prevention of GvHD shortly after transplantation.
Cutaneous T-cell lymphoma (mycosis fungoides). A type of cancer marked by skin lesions and eruptions. Phototherapy can be effective in the early stages of this condition. Lesions may be cleared completely and many patients remain in complete remission for months to years. When relapses occur, they tend to respond as well to phototherapy as the initial lesions.
Polymorphic light eruption. A condition in which an itchy, burning rash and blisters appear on the skin following sun exposure.
Types and differences of phototherapy
The ultraviolet (UV) light spectrum is divided into ultraviolet A (UVA) and ultraviolet B (UVB) light. Broadband UVB has been used to treat skin conditions for many years. It may be used alone, but in many cases, a moisturizing agent or coal tar preparation is applied in a thin layer to the affected area before UVB exposure.
Within the past few decades, the specific spectrum of UVB that affects most skin conditions has been detected. This narrowband UVB is much more effective than broadband UVB for a variety of skin conditions (e.g., dermatitis, psoriasis).
The spectrum of UVA has been subdivided into UVA-1 and UVA-2. UVA-2 is very similar to UVB and is generally not specifically used in phototherapy. Because of its longer wavelength, UVA-1 penetrates more deeply into the skin, affecting mid-and deep-dermal components (including blood vessels) as well as epidermal structures.
Grenz therapy is another form of phototherapy. Other forms of therapy have largely replaced this, making it quite rare today. Instead of ultraviolet light, grenz therapy uses black light to treat minor skin conditions.
Long-wave UVA may be combined with psoralens (PUVA), drugs that increase the sensitivity of the skin to light. This results in therapeutic effects that are not produced with psoralens or UVA alone. Psoralens may be administered orally (e.g., capsules, pills), applied topically (e.g., creams, ointments, lotions) or through bath water. Delivery through bath water provides uniform distribution of the psoralens over the skin surface, very low levels of psoralens in the blood and quick elimination of psoralens from the skin.
Before, during and after phototherapy
Phototherapy is typically performed by a dermatologist. Depending on the type of phototherapy used and how extensive it will be, it may be performed in the dermatologist’s office or in a medical center. It is generally recommended that patients avoid sunbathing before and during phototherapy, and certain medications that affect light sensitivity (e.g., retinoids) may or may not need to be altered. Patients may also be advised to limit alcohol consumption. It is important to follow a physician’s orders.
The doses of ultraviolet radiation used in phototherapy may be determined by the patient’s skin type, but skin type alone does not always reflect the actual sensitivity of a person. Because of this, phototesting may be performed at either a dermatologist’s office or a medical center before phototherapy is recommended. This is done by exposing six small areas of skin that are not usually exposed to the sun (e.g., lower back, buttocks) to a gradually increasing series of light exposure. The doses of light used and the increments between them depend upon the patient’s skin type and the method of phototherapy. Phototesting may take several days. Sunbathing or exposure to sunlamps must be avoided before and during phototesting.
When topical agents are used in combination with ultraviolet B light, they are generally applied for a period of time that varies depending on the agent used. For example, a coal tar preparation is generally left on the skin for about an hour. The agents are typically wiped off of the skin before ultraviolet exposure.
When psoralens plus ultraviolet A light (PUVA) is used, the drugs are administered before light exposure. The delay between the time that the psoralens are administered and the exposure to light depends on the form of application. Oral psoralens are usually taken about 90 minutes before ultraviolet exposure. In bath PUVA, the patient soaks in psoralen-solution bath water for 15 to 20 minutes immediately before exposure.
Depending on the condition treated, the patient may be exposed to light over the entire body surface, only select areas of the body may be exposed, or the patient’s extremities (e.g., arms, legs) may be exposed to higher doses than the trunk.
Ultraviolet light may be administered through a booth, bed (similar to a tanning bed) or handheld device operated by a dermatologist. The genitals are protected, especially in men. Uninvolved skin should also be protected with sunscreen or covered with cloth. The session may take from about 30 minutes to a couple of hours, depending on the type of phototherapy being used and the condition being treated.
Ultraviolet light is generally given in doses that produce slight erythema (redness). With repeated exposures, a gradual increase of the dose is required to maintain this reaction. Protective eyewear is required if psoralens are used. This eyewear must block 100 percent of ultraviolet light and must be worn for 24 hours after the medication has been taken when outdoors, near bright windows or under fluorescent lighting.
Doses may be increased with each successive treatment and the rate of increase depends on treatment frequency and the outcome of the previous treatment. In treatment without psoralens, doses may be increased with every other treatment. In treatment with psoralens, doses are increased no more often than twice a week, at least 72 hours apart, and never in the first week of treatment. If performed properly and in adequate doses, side effects are generally mild. The dermatologist performing the phototherapy will check for these. If intense or painful erythema develops, exposures are stopped until these symptoms disappear.
Usually, phototherapy treatment is continued until complete remission is achieved or no further improvements can be obtained.
Maintenance treatments may lead to longer remission times and are used in the treatment of many conditions, including psoriasis. These may last a few months to a year. The last effective dose is typically given throughout maintenance and, if a relapse occurs during this time, doses are increased again until the condition clears.
To be effective, phototherapy must be given consistently over scheduled periods of time. As a result, it is essential for patients to keep all of their scheduled maintenance appointments. Ideally, treatments should be scheduled for the same time of day.
Repeated skin examinations are very important after phototherapy. These check for any adverse conditions that may develop, such as carcinoma. Such conditions may occur many years after treatment ends.
Although phototherapy sessions usually begin at a medical facility, some patients may be able to continue the treatments at home. Home phototherapy with a prescription light box provides a convenient alternative for patients. However, patients must closely follow their physician’s instructions for use. Failing to adhere to the physician’s schedule can reduce the effectiveness of the treatment. Patients must also be sure to take all of the usual precautions, such as protecting the eyes and genitals. Patients undergoing home phototherapy will also have to visit their physician for regular examinations.
Potential benefits and risks
Phototherapy may significantly improve and even clear many skin conditions. It may help prevent bacterial infections that stem from certain conditions, such as atopic dermatitis. It may reduce the strength of corticosteroids used to treat many conditions or, in some cases, even eliminate the need for them entirely. For example, when psoriasis is treated with psoralens plus ultraviolet A (PUVA) light, no corticosteroids are used. Phototherapy may also increase light tolerance in patients with photosensitive skin.
It is important for patients to understand the potential hazards of ultraviolet radiation, either from natural sunlight or artificial light.
Short-term risks of ultraviolet radiation include:
Severe and sometimes painful erythema (redness)
Burning of the skin, including:
Sunburn reactions
Burning or stinging sensations
Swelling
Blistering
Pruritus (itching)
Increased frequency of recurrent cold sores
Long-term risks of ultraviolet radiation include:
Photoaging, including:
Changes in skin pigmentation
Loss of skin elasticity
Wrinkle formation
Development of cancer, including:
Basal or squamous cell carcinoma
Cancer of the genitals (particularly in men)
It is important to note that phototherapy can trigger flaring of photosensitivity disorders (e.g., lupus). It can also increase the risk of burning in people taking photosensitivity-causing drugs.
The medication psoralen given orally is associated with further risks, including nausea, vomiting, fever, general feelings of illness, and cataract formation (condition in which the lens of the eye becomes cloudy). Because psoralens are absorbed by the lens of the eye, patients must wear protective eyewear that blocks 100 percent of ultraviolet radiation for 24 hours after taking psoralens when outdoors, near bright windows or under fluorescent lighting.
Questions for your doctor
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following phototherapy-related questions:
Why are you recommending that I undergo this procedure?
Are you experienced with phototherapy?
What kind of phototherapy may be beneficial to my condition?
Can you explain the procedure to me in detail?
What risks will I face by undergoing phototherapy?
How will phototherapy affect my other medical conditions?
How will my current medications affect phototherapy?
What precautions should I take when outdoors while on phototherapy?
How long will my phototherapy session last?
Will my phototherapy require maintenance sessions?
