Light Therapy (Phototherapy)

What Is Phototherapy?

Phototherapy — also called light therapy — is the controlled, medically supervised use of ultraviolet (UV) light to treat inflammatory and immune-mediated skin diseases. Unlike natural sun exposure, phototherapy delivers a precise wavelength and dose of UV light to the skin, maximizing therapeutic effect while minimizing unnecessary UV exposure to the rest of the body.

Dermatologists have used phototherapy for over a century, and it remains one of the most effective non-systemic treatments available for a wide range of chronic skin conditions. At Dermatology of Seattle, we offer narrowband UVB (nbUVB) phototherapy — the current gold standard in the field — in an on-site phototherapy booth at our practice.

Phototherapy is an excellent option for patients who have not responded adequately to topical treatments, who wish to reduce or avoid systemic medications (such as biologics or methotrexate), or who prefer a treatment approach that does not require daily application of creams or pills.

How Phototherapy Works

The skin is home to a complex immune network. In conditions like psoriasis, eczema, and vitiligo, immune cells — particularly T-lymphocytes — behave abnormally, driving inflammation and damaging the skin.

Narrowband UVB light at the 311–313 nanometer wavelength penetrates the epidermis and upper dermis, where it:

• Induces apoptosis (programmed cell death) in activated, disease-driving T-cells in the skin
• Suppresses the production of pro-inflammatory cytokines including IL-17, IL-23, and TNF-alpha
• Promotes the release of anti-inflammatory mediators
• Stimulates melanocyte proliferation and migration in vitiligo (restoring pigment)
• Normalizes the abnormally rapid keratinocyte turnover seen in psoriasis

The result is a gradual clearing of plaques, reduced itch, improved skin barrier function, and — in vitiligo — repigmentation of affected areas.

What to Expect: The Phototherapy Protocol

Phototherapy is a course-based treatment that requires consistent commitment to achieve meaningful results. Here is what the process typically looks like:

Who Is a Good Candidate for Phototherapy?

Phototherapy may be appropriate for you if:

• Your skin condition covers a large area of the body and topical treatments alone are insufficient
• You have not responded adequately to topical corticosteroids, vitamin D analogs, or calcineurin inhibitors
• You wish to minimize or avoid systemic medications such as methotrexate, cyclosporine, or biologics
• You are pregnant or breastfeeding and want a non-systemic treatment option
• You have a condition known to respond well to UV light (psoriasis, eczema, vitiligo, CTCL)
• You can commit to the schedule required — 2-3 visits per week for the initial course

Phototherapy is generally not appropriate for patients with lupus, photosensitivity disorders, a history of extensive PUVA therapy, or certain genetic syndromes affecting DNA repair. Your provider will review your full medical history before recommending this treatment.