Phototherapy: What is it? Is it Safe? Uses, Frequency, Dosage and Maintenance

Also known as light therapy, it uses ultraviolet (UV) light for healing effects.


Phototherapy has been used worldwide for almost a century to treat chronic skin conditions such as psoriasis, vitiligo, and severe eczema.

While many treatments decrease the immune system in general, ultraviolet light can be used to reduce the local immune system in the skin. In conditions such as psoriasis, light therapy can also slow down the development of thick, scaly skin.

UV light therapy is used in vitiligo for its additional ability to stimulate melanocytes, the pigment-producing cells of the skin.

This makes phototherapy a good treatment option for almost anyone, especially those who do not like creams, those who want a natural treatment, a steroid-free treatment, and those who wish additional control with a combination of therapies.

Is phototherapy safe?

Dermatologists believe that NB-UVB light therapy is safe when used responsibly. In the few human studies that evaluate this concern, a higher incidence of skin cancer has not been established.

In the most extensive study to date, in which 3867 patients with psoriasis were treated with NB-UVB, with a median of 29 treatments and 352 patients receiving more than 100 treatments, no significant association was found with the cell carcinoma basal, squamous cell carcinoma, or melanoma.


The median of the follow-up period was 5.5 years. However, additional studies are needed to analyze what happens beyond that period.

Targeted therapy is designed to focus the healing light on the affected skin, preventing unnecessary light from passing into the surrounding skin. With recent advances in photomedicine and when used in combination with other therapies, healing can occur earlier and, therefore, reduce overall exposure to UV rays.

Experts agree that an association between NB-UVB and the development of skin cancer is likely. Therefore, there are laws in some countries that require a prescription for these treatments.

So, before using a phototherapy treatment, it is recommended that you analyze all the benefits and possible side effects. Together, you and your doctor can make an informed decision.

How often is phototherapy needed?

Phototherapy treatments are usually given three times a week. In psoriasis, a significant improvement can be seen in two weeks. Most people with psoriasis may need 15 to 20 treatments to achieve clearance and experience a remission rate of 38% after one year.

For people with vitiligo, phototherapy treatment is more complex. The amount of time you have had vitiligo, the locations of the body you want to treat, and the activity of your vitiligo influence the rate of repigmentation.

The response potential is more significant in those who have begun treatment within two years of diagnosis, treated the face and neck, and have stable vitiligo without changes and signs of activity.

Those with signs of active vitiligo justify a more aggressive treatment that often includes full-body phototherapy and oral steroids.

Signs of activity include:

  • Koebner phenomenon.
  • The appearance of trichrome.
  • The appearance of confetti.

But if your vitiligo is not “ideal” for treatment, that does not mean you should not try. The most significant predictor of treatment success is their motivation and consistent combination therapy, including phototherapy and topical therapy.

Most people see the results within 24-36 sessions, although some respond to light therapy more slowly, and changes are observed after 72 sessions.

In general, patients see an average of 50-70% repigmentation of the affected skin after 6 to 12 months of treatment.

Areas with hair follicles, including the face, arms, upper legs, thorax, back, and buttocks, pigment faster and with the best results, while wrists, hands, ankles, and the feet are the slowest to respond.

Repigmentation can be more challenging when white hairs are visible because the pigment-producing cells of origin can be found in the follicle.

Why does the dose change constantly?

During phototherapy, your skin gets used quickly to the dose of energy delivered by NB-UVB. For healing to continue, the amount of light given to specific areas should be continually increased, depending on your skin’s response to therapy.

Because everyone responds differently to phototherapy and different areas of the body respond differently, doctors depend on self-assessment of patients’ skin the day after administering a light treatment.

Personalized education and a careful examination of the photographs helps you decide whether the dose of light (the amount of time you treat an orientation area) should increase, decrease or remain the same.


Your doctor usually recommends maintenance therapy when you achieve your skin’s healing goals. Maintenance therapy involves a plan to reduce the dose or frequency of treatment.

The goal here is to lengthen your time in remission and free time from the condition of your skin.

If your immune system is still overactive or becomes overactive, for example, triggered by stress, illness, trauma, childbirth, or other unpredictable or unknown causes, some degree of more active treatment may be necessary.

In this case, the dose of light therapy and frequency are generally increased.

If you notice any change in your condition, it is essential to discuss these changes with your doctor as soon as you become aware of them, so you can find out what is the best action measure to treat your skin.