Excimer Laser for Targeted Treatment of Psoriasis and Vitiligo

The excimer laser is a laser technology that emits ultraviolet B (UVB) light at a wavelength of 308 nanometers. It is highly effective for chronic skin conditions such as psoriasis and vitiligo, delivering light only to the affected spot without affecting the surrounding skin. At Siam Dermatology, the excimer laser is used for precise and safe treatment.

How does the excimer laser work?

The excimer laser produces an intense UVB beam from xenon chloride gas and delivers energy precisely to the lesion. The mechanism differs depending on the condition.

• Psoriasis: UVB light slows the abnormally rapid growth of skin cells and reduces inflammation.

• Vitiligo: The light stimulates the remaining melanocytes to produce melanin pigment again.

• Key feature: Light is delivered only to the affected area, so the normal skin around it is not exposed to unnecessary UV radiation.

Skin conditions treated with the excimer laser

The excimer laser is approved by the US FDA for treating a number of skin conditions that respond to UVB light.

• Psoriasis: Plaque psoriasis, especially small to medium-sized lesions that do not respond to topical medication.

• Vitiligo: Vitiligo responds very well on the face and neck.

• Atopic dermatitis: Atopic dermatitis (eczema) that is limited to specific areas.

• Other conditions: Alopecia areata and other chronic inflammatory skin conditions that respond to UVB light.

Procedure and aftercare

The doctor assesses the type and severity of the lesions, as well as your skin type on the Fitzpatrick scale, to set the starting energy level. The light is then delivered to the affected spots, a few seconds per spot.

• Frequency: Each session takes about 15-30 minutes. Treatment is usually recommended 2-3 times a week for about 8-16 weeks.

• After treatment: The skin may be slightly red, similar to a sunburn, and this usually resolves within 24-48 hours.

• Care: Apply moisturizer, avoid scratching or scrubbing, and use sunscreen of SPF 30 or higher when going out in the sun.

• When to see a doctor: If you develop blisters or severe pain, tell your doctor right away.

Advantages compared with full-body phototherapy

• Targeted: Light is delivered only to the affected areas, reducing the risk of unnecessary UV exposure to normal skin.

• Faster results: It uses higher energy, so results appear sooner and fewer sessions are needed.

• Convenient: There is no need to undress and stand in a light cabinet. It is more convenient and suits people with lesions in only a few areas.

Frequently asked questions

Does the excimer laser hurt? It is almost painless. You may feel slight warmth or stinging where the light is applied. Anesthetic is not needed.

How many sessions are needed to see results? Psoriasis usually improves within 6-10 sessions, while vitiligo may need 20-30 sessions or more before pigment clearly returns.

Can children be treated? It is safe for patients of all ages, including children, because the light is delivered only to the affected spots. However, you should consult a dermatologist before starting treatment.

Do the results last long? Results may last from several months to several years. However, psoriasis is a chronic condition that may come back, and occasional maintenance treatment helps extend the period of remission.

If you have psoriasis, vitiligo or another chronic skin condition, you can consult a dermatologist at Siam Dermatology to assess whether excimer laser treatment is suitable for you. Call +66 61 448 7000 or LINE @siamderm.

References: Feldman SR, et al. Efficacy of the 308-nm excimer laser for treatment of psoriasis. J Am Acad Dermatol. 2002;46(6):900-906. / Spencer JM, et al. Excimer laser for vitiligo. Arch Dermatol. 2004;140(10):1258-1262.

Written by Dr. Patara Voravutinon, Dermatologist · Last reviewed July 16, 2026