by Diane A. Safer, PhD
Phototherapy uses lightwaves to treat certain skin conditions. The skin is exposed to an ultraviolet (UVB or UVA) light for a set amount of time. Phototherapy uses a man-made source of UV light. UV light also comes from the sun. UVA treatment is usually combined with a medication called psoralen, the procedure is known as psoralen UVA (PUVA). The choice of treatment may depend on the condition being treated.
This topic does not cover phototherapy for jaundice in babies.
Reasons for Procedure
UV light shuts down immune system cells in the skin. It can help in skin conditions that are caused by an overreaction of the immune system. Skin conditions that are treated with phototherapy include:
The UV lights may negatively affect your skin in a number of ways, including:
PUVA treatment may also cause:
If you have received a great number of phototherapy treatments, you may be at risk for:
Factors that may increase the risk of complications include:
What to Expect
Prior to Procedure
You will be asked to remove any clothes that cover the skin being treated. Areas that do not need treatment should be covered and protected as much as possible. Some safety steps include:
Make sure to inform your doctor about any medication that you are currently taking. Some medications, including over-the-counter medication, can increase the risk of side effects.
Description of the Procedure
Types of phototherapy include:
Treatment over a large area may be treated in a treatment unit. You can stand in this unit during treatment. Smaller areas may be treated with smaller units. A laser treatment will use a laser light that is focused on the specific area.
How Long Will It Take?
The first treatment is usually very short, even a few seconds. Your phototherapy sessions will vary in length. It will depend on your skin type and the strength of the light chosen by your doctor. Treatments rarely last longer than a few minutes.
Generally, several treatments are required each week. The length of treatment will depend on the type of phototherapy:
Treatments will continue until your skin is clear. Sometimes, occasional maintenance treatments are needed. The maintenance sessions can usually be done in your doctor’s office or with a home UV light unit.
Will It Hurt?
You may feel a warm sensation on your skin, similar to a mild sunburn. Your doctor can recommend medication if you have discomfort after treatment.
It is important to avoid natural sunlight when you are receiving UV light treatment:
Your doctor should regularly examine your skin for skin cancer. UV light exposure from sunlight causes skin cancer. Long-term PUVA treatment can also increase the risk of skin cancer. No studies have found a direct link from nbUVB phototherapy to skin cancer.
Call Your Doctor
Contact your doctor if your recovery is not progressing as expected or you develop complications, such as:
If you think you have an emergency, call for medical help right away.
American Academy of Dermatology
National Psoriasis Foundation
American Academy of Dermatology’s newest guidelines for the management of atopic dermatitis focus on treatments. American Academy of Dermatology website. Available at: https://www.aad.org/media/news-releases/american-academy-of-dermatology-s-newest-guidelines-for-the-management-of-atopic-dermatitis-focus-on-treatments. Accessed December 18, 2017.
Indications for phototherapy. Derm Net AZ website. Available at: https://www.dermnetnz.org/cme/phototherapy/indications-for-phototherapy/. Updated November 10, 2014. Accessed December 18, 2017.
Phototherapy. National Psoriasis Foundation website. Available at: https://www.psoriasis.org/about-psoriasis/treatments/phototherapy. Accessed December 18, 2017.
Psoriasis. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T116742/Psoriasis . Updated December 4, 2017. Accessed December 18, 2017.
Psoriasis: General principles for phototherapy. American Academy of Dermatology website. Available at: https://www.aad.org/practicecenter/quality/clinical-guidelines/psoriasis/phototherapy-and-photochemotherapy. Accessed December 18, 2017.
UVA photo(chemo) therapy. Derm Net AZ website. Available at:
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Accessed December 18, 2017.
UVB phototherapy. Derm Net AZ website. Available at: https://www.dermnetnz.org/cme/phototherapy/uvb-phototherapy/. Accessed December 18, 2017.
Last reviewed November 2018 by EBSCO Medical Review Board Michael Woods, MD, FAAP