Narrowband UVB Phototherapy for Psoriasis: How It Works and What You Can Expect from the Treatment

Updated on April 29, 2021, by Don Mehrabi

Psoriasis is a complex inflammatory condition affecting about 2% of Americans. Patients develop characteristic skin lesions that respond variably to treatment. Mild cases involve limited areas of the skin. Severe ones present with widespread plaques and may affect the joints and other organs.

Psoriasis Plaques on the Lower Limbs.


Narrowband (NB) UVB phototherapy is the treatment of choice for moderate to severe psoriasis. In this procedure, ultraviolet (UV) light of a specific wavelength and energy level is used to reduce excessive skin inflammation and thickening. It is highly effective and safe if done properly.

In this article, we explain how NB-UVB phototherapy works on psoriasis. We also discuss its advantages and disadvantages compared to other treatments, as well as what to expect during your sessions.

What Is Psoriasis?

Psoriasis is a medical condition that primarily affects the skin. Its cause is poorly understood, but genetic and autoimmune mechanisms are thought to be in play. Advanced cases involve the joints–a condition known as “psoriatic arthritis”—and other organs.

Your doctor can diagnose the condition based on the typical skin lesions: reddish plaques with well-defined borders and silvery-white scales. A biopsy may be necessary at times to confirm the diagnosis and rule out other skin disorders. Psoriasis plaques bleed easily when the scales are removed. More than half of patients develop scalp or nail psoriasis as well.

The management includes systemic agents and topical treatments, both of which suppress the immune system and abnormal skin growth. NB-UVB phototherapy is the standard of care for stable lesions involving at least 10% of the body surface and non-pustular psoriasis appearing on the palms and soles.

How Does NB-UVB Phototherapy Help Psoriasis?

UV radiation has enough energy to do the following on psoriasis lesions:

  • Reduction of immune cell activity, particularly of the helper T-cells T1 and T17, which inflame the skin and induce the formation of psoriasis plaques.
  • Inhibition of the FOXP3+ cells, a group of T-cells that activate the entire immune system.
  • Induction of cell death (apoptosis) in some types of immune and skin cells.

By targeting the immune system, the results are quick and may last for several months.

The UV light spectrum is divided into several bands:

  • UVA has the longest wavelength at 315-400 nanometers. It has the lowest energy, though it penetrates the dermis.
  • UVB has a wavelength of 280-315 nanometers. It does not penetrate the dermis.
  • UVC and extreme UV are light beams with much higher energy and are not used medically. UVC has a wavelength of 100-280 nanometers. Extreme UV is the shortest, with a wavelength range of 10-100 nanometers.

Of these UV bands, UVB light is the most widely used for psoriasis treatment. It has the following advantages:

  • UVB does not require light-sensitizing agents, helping you reduce costs and avoid side effects.
  • UVB phototherapy can combine safely with other psoriasis treatments, as they do not produce harmful chemical reactions together.
  • UVB light therapy is more cost-effective than others for moderate to severe psoriasis. 
  • On its own, UVB treatment has a low risk of causing serious side effects. It is considered safe for pregnant women.
  • The procedure is widely available in the US.

UVB phototherapy was first used as early as the 1920s when the Goeckerman treatment was developed. The said regimen required coal tar application on the affected areas before exposing them to a broadband UVB (BB-UVB) light source. BB-UVB works within the 290-320-nanometer range. However, it became obsolete in the 1980s with the advent of narrowband UVB (NB-UVB) phototherapy, which used only light within the 311-313-nanometer range.

Narrowing the UVB light band has two advantages. First, eliminating lower-energy beams makes the procedure more effective. Second, the restricted wavelength range prevents energy fluctuations that can burn the skin and lead to other adverse events. At BHSkin Dermatology, patients with moderate to severe psoriasis receive NB-UVB treatment.

UVA, which has lower energy, is also used for managing psoriasis plaques. However, it needs light-sensitizing agents, typically psoralens, to work. This modality is thus called “Psoralen plus UVA phototherapy” or “PUVA phototherapy.” The main disadvantages of PUVA therapy are:

  • Psoralens are of limited availability in the US. Methoxsalen is the only psoralen approved by the US-FDA.
  • PUVA phototherapy poses a higher risk of developing skin cancer, e. g. melanoma.

For these reasons, PUVA therapy is usually reserved for pustular psoriasis and resistant plaques, both of which need more aggressive regimens.

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What Can You Expect When Receiving NB-UVB Phototherapy?

When you visit a BHSkin Dermatology clinic, your doctor will conduct a thorough examination to see if NB-UVB treatment is appropriate for you. Here are other things you can expect during your consults:

Before the Treatment

It is important to tell your dermatologist all information that can impact your treatment. UV light therapy, regardless of the type, is not entirely without risks.

If your doctor decides that UV light therapy is right for you, they will choose the wavelength appropriate for your skin condition and type. This enhances the procedure’s effectiveness and safety.

All psoriasis patients are advised to avoid excess skin drying and potential irritants. When you’re scheduled for NB-UVB phototherapy, you may also be asked to avoid sun exposure and some drugs several days before starting your treatment regimen. This reduces UV light sensitivity and burning. Cold sore medication may be necessary if you’re prone to developing cold sores.

During the Treatment

In every session, you will be asked to maximize skin exposure while standing inside the treatment booth. You will be given protective glasses to avoid eye injury during the procedure. NB-UVB phototherapy does not require numbing medication, although it can make you feel warm. Your doctor may give your treatment in divided doses if you cannot tolerate the temperature.

Each session lasts for about 15-20 minutes, depending on psoriasis severity. On average, NB-UVB phototherapy costs $3,500-4,000 annually per patient. This is cheaper than PUVA phototherapy, biologic treatments and most systemic drug regimens.

NB-UVB therapy is contraindicated in the presence of heart disease, stroke, bleeding disorders and pre-existing skin cancer. Also, you must avoid the following medications while receiving the treatment as they can induce photosensitivity:

  • Antibiotics classified as tetracyclines, sulfonamides and fluoroquinolones. Examples are minocycline acne treatments and Bactrim and Cipro for urinary tract infection.
  • Non-steroidal anti-inflammatory drugs like aspirin and ibuprofen.
  • Vitamin-A-containing medications like Tazorac and Accutane.
A Phototherapy Booth

After the Treatment

NB-UVB therapy has no downtime. You may experience mild skin discomfort after your session, but this should not hold you back from your usual activities.

The regimen is intensive. You may need 2-3 sessions weekly over 2-3 consecutive months. Committing to your treatment schedule will produce the best results. You may notice vast improvements in as early as 2-4 weeks.

The following are the most common short-term side effects of NB-UVB therapy:

  • Redness
  • Swelling
  • Itching
  • Discomfort
  • Bruising
  • Blistering
  • Crusting

Any one of these may develop within the first 24 hours after a session. They are normally mild and go away on their own. Your doctor may prescribe a treatment cream to minimize these side effects.

Generally, UV light therapy has the following risks when used long-term:

  • Pigmentation problems
  • Skin aging
  • Cataracts
  • Skin cancer

That is why clinicians limit the course of treatment to only one per year.

However, the health risks of NB-UVB phototherapy become significant only if it is not done properly or the patient is not examined completely. It is important to choose the right dermatologist to perform this procedure so you may be treated with a keen eye. At BHSkin Dermatology, our skin experts always ensure that each therapy is effective and safe for patients.


In summary, psoriasis is a medical condition mainly affecting the skin. Nail and scalp psoriasis are also common among patients, with some developing complications in the joints and other organs. It is presumed to have genetic and autoimmune causes. NB-UVB phototherapy is a safe and effective treatment for moderate to severe psoriasis. It targets the immune system, producing long-lasting results in a short time.

NB-UVB phototherapy has considerable advantages over other psoriasis treatments. Aside from its effectiveness and safety profile, it is also cost-efficient and widely accessible. UVA light therapy is an alternative that uses light beams of lower energy but needs psoralen pretreatment to work. The regimen can clear psoriasis plaques but may also lead to some serious side effects. PUVA therapy is thus reserved for pustular lesions and resistant cases.

Stress No More over Psoriasis! Let LA’s Top Skin Doctors Zap It Away!

Psoriasis affects mostly young adults, but it can strike at any time during your prime. The scaly plaques can bleed and grow wide on any skin part, concealed or exposed, causing distress for many patients.

Not to worry! At BHSkin Dermatology, our board-certified skin experts clear psoriasis lesions skillfully and routinely, like no other. Visit us now at our clinics in Encino and Glendale to get a full examination and the best treatment plan. You may also use our virtual portal if you prefer to consult with our doctors remotely.

Book your appointment today and get clearer skin in no time!



Author: Don Mehrabi

Don Mehrabi, MD, FAAD, is LA’s leading board-certified dermatologist who treats patients, builds the BHSkin clinics, and raises three kids. This blog builds on medical studies combined with Dr. Mehrabi's first-hand experiences from practicing in Encino-Tarzana, Glendale, and online

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