Ultraviolet Light Therapy: Everything You Need to Know

An Option for Some Medical and Skin Conditions

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Medical ultraviolet therapy, also described as phototherapy, is a type of intervention used for treating several conditions, including certain skin infections, inflammatory disease, and cancer. The dose and method of treatment differ depending on the illness that’s being treated.

Often, phototherapy is used as an adjunctive treatment, along with other medications or therapies, rather than as the only method of treatment. Your healthcare provider might also prescribe a specific medication for you to take before each treatment to maximize the benefits of ultraviolet light therapy. 

Nurse using light therapy on patient

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What Is Ultraviolet Light Therapy? 

Ultraviolet light therapy is the use of ultraviolet light to destroy infectious organisms or harmful cells that cause disease of the body—especially superficial lesions and skin infections. Ultraviolet light is naturally emitted from the sun, but it can also be channeled for treatment with specially designed devices.

Light has different wavelengths. The wavelengths most commonly used in therapeutic ultraviolet light treatments are longer wavelength UVA light and shorter wavelength UVB light.

Several mechanisms are involved in medical ultraviolet light treatment. Ultraviolet light can damage human cells—both healthy cells and harmful cells. It is believed that the therapeutic effects are due to inducing an oxygenation reaction that may preferentially destroy certain cells, such as the autoimmune inflammatory cells seen in lupus.

Ultraviolet light is also germicidal. This is why it can be used to eradicate some infectious organisms on the skin.

Generally, ultraviolet light treatment is repeated several times per week for a few months. You would have the calibrated light directed to the lesion (or lesions) on your skin for several minutes at a time for each treatment.

Your healthcare provider might prescribe psoralen if you are having treatment with UVA light. This medication makes the skin more sensitive to ultraviolet light. 


This treatment might be unsafe for you if your skin is especially sensitive to light.

Even though one type of skin cancer can be treated with ultraviolet light therapy, your healthcare provider might recommend against this treatment approach if you have had skin cancer that can be caused by ultraviolet light exposure. 

If you are taking medications that increase sun sensitivity, like tetracycline or retinoids, you would need to stop taking them for several weeks before your treatment. The increased skin sensitivity to sunlight caused by these medications would make ultraviolet light harmful for you, not beneficial. 

Potential Risks 

Ultraviolet light treatment can cause complications, and the pretreatment also poses a risk. Exposure to ultraviolet light can cause skin redness and itching, and it may lead to severe sunburn. Repeated eye exposure can increase the risk of cataracts.

If you take the pretreatment medication, you will be more sensitive to light, including natural sunlight. When taking this medication, you can have an increased risk of sunburn or eye damage. 

Purpose of Ultraviolet Light Therapy 

This treatment is used to manage certain skin diseases and infections. It can result in improvement of your symptoms, and it can cure certain skin infections. However, when used for chronic inflammatory disease, the effects of ultraviolet light therapy might be temporary, and the condition can recur months or years after treatment is stopped. 

Conditions treated with ultraviolet light therapy include: 

Ultraviolet light therapy is considered a first-line therapy for CTCL and Sézary Syndrome, and a second-line therapy for mycosis fungoides and graft versus host disease.

This treatment can prolong survival in CTCL, but outcomes are not as easily measured when it comes to skin conditions that cause discomfort and unwanted changes in the skin’s appearance, like psoriasis.

Ultraviolet light therapy has also been studied for treatment of lupus, a systemic inflammatory disease that causes a range of symptoms. Additionally, it has been used for the treatment of seasonal affective disorder, a mood disorder that is associated with lack of sunlight.

How to Prepare

If you and your healthcare provider are considering ultraviolet light therapy as a treatment for your condition, your practitioner may send you for a pretreatment eye examination to see if you have cataracts. 


You will have your ultraviolet light treatment in your dermatologist’s office. This is an outpatient procedure. Your appointment should take approximately an hour—including the registration process, pre-treatment skin examination, and procedure.

What to Wear

You should wear clothes that are comfortable and that aren’t too difficult to take off and put back on after your therapy session. 

You may be asked to change into a hospital gown during your treatment, or you might be able to wear your regular clothes and to just expose the area on your skin that needs to be treated. 

Food and Drink

You shouldn’t have to make any specific adjustments to your diet before your ultraviolet light therapy session. However, if you tend to break out in a rash or develop any skin reactions from certain foods or drinks, you should avoid these items for at least a week before your ultraviolet light treatment. 


If you are prescribed psoralin pretreatment, you will need to take it as directed by your healthcare provider.

What to Expect During the Procedure

If you are prescribed ultraviolet light therapy, you would visit your dermatologist’s office for each treatment. When you go in for your treatment, your practitioner may examine your skin or ask you about your symptoms to assess any changes in your condition. 

Your healthcare provider will use a machine that is calibrated to emit the wavelength of ultraviolet light you need for your treatment. For treatment of most skin conditions, a selected area of your skin would be exposed to the ultraviolet light for a pre-determined duration.

For treatment of some conditions, you would be directed to sit near the device for more widespread treatment. Your treatment would last for about 10 to 30 minutes at a time.

Ultraviolet light therapy does not involve incisions, creams, or sutures. You will not need any pain control.

You will be asked to expose the area of skin that needs to be treated. You might also have a covering placed on exposed areas of your skin that are not being treated, and you will be asked to wear goggles to protect your eyes.

You should be able to leave the practitioner's office right after your treatment. However, if you experience any discomfort, be sure to tell your healthcare provider so they can assess your complaints and treat any problems (like a skin burn). If you've had a side effect, your practitioner might make adjustments to your therapy plan as necessary. 


If you are having ultraviolet light treatment on a regular basis for several months, you can be very susceptible to sun-induced sunburn throughout your treatment course. 

You may be instructed to avoid exposure to sunlight for several days after each treatment or to use sunscreen when you go outside.

A Word From Verywell 

Ultraviolet light therapy might be part of the treatment plan that your healthcare provider prescribes for you. This treatment is generally considered safe and effective, but there are precautions and potential side effects. Be sure to follow all of the recommended safety guidance so you can minimize the risks of this treatment. 

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Olsen EA, Hodak E, Anderson T, et al. Guidelines for phototherapy of mycosis fungoides and Sézary syndrome: A consensus statement of the United States Cutaneous Lymphoma Consortium. J Am Acad Dermatol. 2016;74(1):27-58. doi:10.1016/j.jaad.2015.09.033

  2. Ahmed I, Fang Y, Lu M, et al. Recent patents on light-based anti-infective approaches. Recent Pat Antiinfect Drug Discov. 2018;13(1):70-88. doi:10.2174/1872213X11666171108104104

  3. Singer S, Berneburg M. Phototherapy. J Dtsch Dermatol Ges. 2018;16(9):1120-1129. doi:10.1111/ddg.13646

  4. McGrath H Jr. Ultraviolet-A1 irradiation therapy for systemic lupus erythematosus [published correction appears in Lupus. 2017 Dec;26(14):1573]. Lupus. 2017;26(12):1239-1251. doi:10.1177/0961203317707064

  5. Yin R, Dai T, Avci P, et al. Light based anti-infectives: Ultraviolet C irradiation, photodynamic therapy, blue light, and beyond. Curr Opin Pharmacol. 2013;13(5):731-762. doi:10.1016/j.coph.2013.08.009

  6. American Academy of Dermatology. Laser and lights: how well do they treat rosacea?

  7. Hodak E, Pavlovsky L. Phototherapy of mycosis fungoides. Dermatol Clin. 2015;33(4):697-702.doi:10.1016/j.det.2015.05.005

  8. Cho A, Jantschitsch C, Knobler R. Extracorporeal photopheresis-An overview. Front Med (Lausanne). 2018;5:236. Published 2018 Aug 27. doi:10.3389/fmed.2018.00236

By Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.