What is Narrowband Ultraviolet B light treatment?

Narrowband Ultraviolet B (UVB) is a type of ultraviolet light (UVL) treatment. Ultraviolet light is widely recommended by dermatologists for several skin disorders including (but not limited to):

  • Psoriasis
  • Eczema
  • Nodular
  • Prurigo
  • Mycosis Fungoides
  • Polymorphic Light Eruption (PLE)
  • Vitiligo

The choice of UVL over other forms of treatment depends on a range of factors including skin condition, type, previous treatments, and current medication. Your doctor will discuss with you what is best for you.

Ultraviolet light treatment is not a long-term cure, but it can improve your skin condition significantly for a period.

What is involved in Narrowband Ultraviolet B light treatment?

We use a Narrowband UVB machine (TL01) - a large cabinet with panels of fluorescent tubes – for the treatment. We will show you the machine before your treatment starts and discuss the days and times of your treatment with you. Treatment is usually three times a week (Monday, Wednesday, and Friday) for up to 16 weeks.

You will need to commit to attending all the sessions within the prescribed course for the treatment to be as successful as possible.

Your first appointment

Prior to starting your treatment course, a mild erythema dose (MED) test may be performed to determine a more accurate starting dose of UVB for you. This is done using a small, hand-held device which is applied to an area of your skin (usually your upper back) for a set amount of time (approximately one minute).

A skin marker will then be used to trace the border of the device onto your skin, so the test area is easily identifiable for ease of reading. Try to keep this area as dry as possible before and after the appointment and do not scrub this area of skin to avoid irritation and a false reading.

You will then need to return to the clinic the following day at the time of your usual treatment so we can take the test reading. Your start dose of UVB will be determined at this time and you will receive gradually increasing doses in the light machine depending on how your skin is affected each treatment.

During the procedure

Before starting the treatment, the nurse will explain the procedure to you including how you should stand in the light cabinet and what protective clothing/equipment should be worn. It is a full body treatment; therefore, clothing (apart from a dark-coloured sock for male patients) is not usually worn in the machine unless otherwise specified by phototherapy staff.

Initially, treatment only takes around half a minute and may increase to a maximum of 14 minutes depending on your skin type, skin condition and your response to the previous treatment.

Following treatment, it is not unusual to develop mild skin pinkness. Please tell the nurse at your next appointment if, a few hours after treatment, you felt hot, uncomfortable or your skin became red.

Your eyes may be shielded by goggles during treatment. If your skin condition is affecting the eyelids, we can treat this area, however eyelids must remain closed throughout the duration of treatment administration.

A full-face visor is used if your face does not require any treatment or if you are experiencing sensitivity to this area.

Risks and side-effects

We make every effort to avoid problems, but occasionally side effects can occur:

Short-term side effects


After any treatment session, if your skin becomes pink or red, blistered, hot or uncomfortable (e.g., like sunburn) report it to the phototherapy nurse at your next appointment. If symptoms are severe, please contact the phototherapy nurses as soon as possible on 020 8216 5770.

If out-of-hours (after 5.40pm and before 8am), please ring the hospital switchboard on 0208 216 4600 and ask to speak to the on-call dermatologist at the Royal Free 3 Hospital for advice; or go to A&E and take this leaflet with you. We may stop the treatment until your symptoms settle.

Dry skin

Your skin may be drier than usual during treatment and for some time afterwards. Applying an emollient to the whole skin at least twice a day and up to four times will help keep the skin hydrated and soft.


UV therapy can cause itching, particularly during the first two weeks. Applying plenty of emollients or taking over-the-counter antihistamines will help alleviate the itching. Please let the nursing staff know if you choose to take antihistamines during your treatment course.

Cold sores (herpes simplex virus)

Patients who have had cold sores in the past may get a repeat infection. Apply sunscreen to the lips before every treatment to help prevent this.


Small pustules (pus-filled spots) and minor inflammation around the hair follicles can occur. This does not cause discomfort, and treatment can continue. Applying moisturiser at least half an hour before treatment and in a downward motion (in the direction of your hair growth) to your whole body prior to treatment may help to prevent this.


If you sometimes develop a rash (e.g., prickly heat) from light exposure, you may experience a flare-up with the UV treatment. If this happens, tell the phototherapy nurse or doctor who may be able to treat you to reduce the symptoms.


You may notice a tan developing during your treatment. The tan will gradually fade back to your normal skin tone following treatment.

Long-term side effects


Frequent exposure to UV may cause ageing changes in the skin, such as freckles and wrinkles.

Skin cancer

Sun exposure can increase the risk of skin cancer. This possible increased risk can also occur if you receive high amounts of UVB treatment (more than 300 treatments). There is a limit to the amount of UV therapy you can have in your lifetime (300 treatments). We keep records to avoid exceeding the recommended amount. Please ask the nurse or doctor if you want more information.

What you need to do during your treatment

  • Dry, flaky skin can prevent UV absorption and reduce the effectiveness of treatment. On treatment days, please apply a suitable moisturiser from the list provided on the ‘Using topical treatments alongside Phototherapy’ leaflet. Avoid tar, steroid and vitamin preparations. After treatment and on non-treatment days, regularly apply plenty of moisturiser, as well as your topical treatments.
  • On treatment days, do not wear make-up or use perfumed products, aftershave, or cosmetics before your treatment. You can apply them after treatment.
  • Always inform the nurse if you are taking, or about to start, new medication or creams as these may affect your reaction to your treatment.
  • Over the period of your treatment do not use a sunbed or sunbathe. On brighter days, protect exposed areas of skin from sunlight by wearing a hat, long sleeves and seeking shade where possible. Sunblock may be applied on non-treatment days.
  • Ideally, all jewelry should be removed for the treatment to avoid burning newly exposed sites. If you are unable to remove any jewelry, please discuss this with the phototherapy team who will advise you accordingly.
  • Avoid haircuts or hairstyle changes whilst having treatment. Please discuss this with the team if this is a problem.
  • Men need to cover their genitals with a dark-coloured sock for every treatment.
  • Some plants, vegetables, and fruits (e.g., celery, parsnips, figs, and limes) have photosensitisers in them. These can make you more sensitive to UV light, so please avoid handling them for at least two hours before treatment.
  • Please report to phototherapy staff if you experience any discomfort while you are in the machine.

Regular and punctual clinic attendance is important. Please be on time for your appointment as we may not be able to accommodate late arrivals. If you are unable to attend for treatment, telephone the phototherapy unit on 020 8216 5770 to let the staff know.

Alternatively, telephone the dermatology reception on 020 8216 4831 on non-treatment days and leave a message. If you miss three appointments without notifying us, it will be considered an automatic discharge from the Phototherapy service.