Phototherapy is the use of light for treatment of a disease. For dermatology, ultraviolet-B (UVB) or ultraviolet A (UVA) generating lamps are  generally used.  While the sun also emits  UVB and UVA radiation thereby providing some benefit to certain skin disorders, artificial UV light sources offer the advantage of reliable and regulated dosing.  UVA light is administered with a drug called psoralen. This drug helps make UVA light effective. This form of treatment is more popularly called PUVA or photochemotherapy.  UVB on the other hand is effectively used alone. 

How  does phototherapy work?

Both UVB and UVA light generally work by controlling the immune processes that trigger many inflammatory and some proliferative skin disorders .  Pigment production is  also stimulated. 

What are the skin diseases responsive to phototherapy?

Phototherapy is commonly used for inflammatory skin diseases such as psoriasis, exfoliative dermatitis,  atopic dermatitis, chronic eczemas, pityriasis rosea, pityriasis lichenoides and parapsoriasis.  It is also used for vitiligo, early cutaneous T cell lymphoma (mycosis fungoides) and generalized itching associated  with chronic kidney or liver disease.

Topical medications for widespread skin involvement with the above diseases may no longer be practical and safe.  While oral drugs may help, not all patients can tolerate their side-effects or have contraindications for their use.  Furthermore, standard forms of treatment do not always work in all patients. Phototherapy in these cases is a good option.   Combination treatments may also be utilized to hasten treatment response.

How safe is phototherapy? What are its side effects?

Like significant exposures to the sun, phototherapy may immediately cause a sunburn experience and tanning or skin darkening.   These are  reversible.  Many years of repeated ultraviolet light exposure may lead to  premature skin aging and skin cancer. Especially prone to these long-term effects are fair-skinned individuals. Generally phototherapy courses for inflammatory skin disorders  only last a few months.

UVB in particular narrow band UVB light can be safely administered  to children and pregnant women. 

What does the phototherapy procedure entail? What should one expect?

The affected skin is exposed to the ultraviolet lamps for a few minutes. The duration may progressively increase with subsequent exposures depending on the patient’s response. The patient may be asked to apply moisturizers prior to the treatment exposure.  PUVA therapy will require ingestion of the drug psoralen two hours prior to the UVA exposure. Treatment sessions are scheduled usually on a thrice weekly basis. Depending on the disease indication, average treatment sessions may range from 20 to 30. Some cases, especially vitiligo may require more than 6 months of continued treatment.  Other cases may continue to benefit from phototherapy administered less frequently with longer intervals in between exposures.

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