Dermatologists use light therapy, also known as phototherapy, as a targeted medical treatment for a range of skin conditions. This approach harnesses specific wavelengths of ultraviolet or visible light to reduce inflammation, slow abnormal cell growth, and control bacteria on the skin. It is a well-studied, non-invasive option often prescribed when topical treatments are insufficient or when patients prefer to avoid systemic medications.
How Light Therapy Works in Dermatology
The core principle behind phototherapy is that different wavelengths of light penetrate the skin to different depths and trigger distinct biological responses. For example, UVB light primarily affects the upper layers of skin, where it can suppress the overactive immune cells driving conditions like psoriasis. UVA light, often combined with a photosensitizing agent in a treatment called PUVA, reaches deeper layers. Narrowband UVB (311-313 nm) is a commonly used, highly effective form of UVB therapy that delivers a precise band of light to maximize benefits while minimizing risks.
Common Skin Conditions Treated with Light Therapy
- Psoriasis: Phototherapy slows the rapid turnover of skin cells and reduces inflammation, helping to clear plaques.
- Eczema (Atopic Dermatitis): Light therapy can calm inflammation and itching, especially for moderate to severe cases that do not respond well to topicals.
- Vitiligo: Narrowband UVB can help stimulate pigment-producing cells (melanocytes) to repigment white patches of skin.
- Cutaneous T-Cell Lymphoma (a type of skin lymphoma): Phototherapy may be used to manage the skin symptoms of this rare condition.
- Acne: Blue light therapy targets Propionibacterium acnes bacteria on the skin, while red light reduces inflammation in acne lesions.
Key Types of Light Therapy Used by Dermatologists
Dermatologists select the specific type of light therapy based on the condition, skin type, and patient history. In-office treatments are typically prescribed two to three times a week for a defined course, often with careful dose adjustments to minimize side effects like sunburn-like reactions.
UVB Phototherapy
This includes both broadband UVB and the more common narrowband UVB. It is a first-line treatment for psoriasis, vitiligo, and other inflammatory diseases. Treatments are delivered in a cabinet lined with light tubes, and the patient stands or sits inside for exposure lasting from seconds to a few minutes, depending on the dose.
PUVA Therapy (Psoralen + UVA)
In this treatment, the patient takes or applies a photosensitizing drug called psoralen before exposure to UVA light. Psoralen makes the skin more responsive to the light, allowing for a more potent effect. PUVA is effective for severe psoriasis, hand and foot eczema, and early-stage cutaneous T-cell lymphoma.
Targeted Light Therapy (e.g., Excimer Laser)
For small, stubborn patches of psoriasis or vitiligo, a device like the excimer laser delivers high-intensity UVB light precisely to the affected area, sparing surrounding healthy skin. This can reduce the number of treatments needed and lower cumulative light exposure.
Blue and Red Light for Acne
In-clinic devices use blue light to kill acne-causing bacteria and red light to reduce inflammation and encourage healing. These are often used as part of a comprehensive acne treatment plan and may require multiple sessions.
Safety and Side Effects
When administered and monitored by a board-certified dermatologist, light therapy is a well-tolerated treatment. Common short-term side effects can include mild redness, skin dryness, or a sunburn-like sensation. Long-term use of PUVA, and to a lesser extent UVB, carries a slightly increased risk of skin cancer, which is why dermatologists carefully track cumulative doses and perform regular skin exams. Protective eyewear is always worn during treatments to protect the eyes from UV damage.
What to Expect During In-Office Phototherapy Sessions
- Evaluation: Your dermatologist will assess your skin type, condition severity, and medical history to determine if phototherapy is appropriate.
- Patient Education: You will receive guidance on how to prepare for sessions, including avoiding sun exposure and not using photosensitizing products.
- Dosing: The initial light dose is low and gradually increased over subsequent visits, based on how your skin responds.
- Protection: You will wear special goggles and, if needed, cover sensitive areas such as the genitals or lips during treatment.
- Monitoring: The dermatology team will check for any adverse reactions and adjust the treatment plan as needed.
Light therapy is a powerful tool in the dermatologist’s arsenal, offering a safe, effective option for many chronic skin conditions. It is not a one-size-fits-all solution, but when used under expert supervision, it can provide significant relief and improved quality of life. For personalized advice on whether phototherapy is right for you, consult a board-certified dermatologist.