Light Therapy (Phototherapy) for Psoriasis: UVB & Laser
Phototherapy, also referred to as light therapy, is a first-line treatment for moderate to severe plaque psoriasis. It uses ultraviolet (UV) light to decelerate the overproduction of skin cells and curb inflammation. For decades, dermatologists have employed UV radiation to manage flares and achieve sustained clearance. Today, advanced modalities such as narrowband UVB and excimer lasers deliver targeted benefits with fewer adverse effects.
This approach works by exposing the skin to specific UV wavelengths. The most common is narrowband UVB (311–313 nm), which is more effective and safer than older broadband UVB. PUVA (psoralen plus UVA) is another option that combines a light-sensitizing agent with UVA. For localized plaques, excimer lasers deliver focused UVB to small areas, limiting exposure to healthy skin. These procedures are typically conducted in a dermatologist's office or a dedicated phototherapy center.
Understanding Phototherapy for Psoriasis
Psoriasis is a chronic autoimmune disorder marked by accelerated skin cell turnover, resulting in thick, scaly patches. UV light penetrates the skin and dampens overactive T-cells, thereby reducing inflammation and slowing cell production. The exact mechanism involves inducing apoptosis in skin cells and local immunosuppression.
Several types of phototherapy are available:
- Narrowband UVB (NB-UVB): The most common type, emitting 311-313 nm wavelengths. It is effective for widespread psoriasis and has a low risk of burning.
- Broadband UVB: Older form, less commonly used due to higher burning risk and lower efficacy.
- PUVA: Combines UVA with oral or topical psoralen. Very effective but carries higher skin cancer risk.
- Excimer Laser: Delivers focused UVB to stubborn plaques without affecting healthy skin. Ideal for scalp, elbows, and knees.
Tip: Consistency is key for phototherapy. Most patients require 2–3 sessions per week for 1–3 months to achieve clearance. Maintenance sessions may be needed to prevent relapse.
Phototherapy is frequently employed when topical agents (corticosteroids, vitamin D analogs) are ineffective or impractical for large body surface areas. It can also be combined with systemic medications or biologics for enhanced results. Your dermatologist will determine the best regimen based on your skin type, disease severity, and medical history.
Benefits and Risks of UV Light for Psoriasis
One of the main advantages of phototherapy is its long-term safety compared to systemic drugs. It does not suppress the entire immune system, avoiding risks like infections and organ toxicity. Additionally, UVB therapy can improve secondary conditions like vitiligo and eczema. Patients often report relief from itching and improved quality of life.
However, there are side effects. Short-term effects include sunburn-like redness, blistering, and dry skin. Long-term risks, especially with PUVA, include premature skin aging and increased risk of skin cancer (melanoma and non-melanoma). Narrowband UVB is considered safer but still requires careful monitoring. Eye protection is mandatory to prevent cataracts.
Warning: Never attempt to use tanning beds for phototherapy. They emit mostly UVA and inadequate UVB, increasing skin cancer risk without therapeutic benefit. Only use medical-grade devices under a doctor's supervision.
Who is a good candidate? Up to 80% of patients with plaque psoriasis respond well to UVB treatment. It is particularly suited for those with widespread patches (covering >10% body surface area) or for individuals who cannot tolerate medications. Contraindications include photosensitive disorders (e.g., lupus), history of skin cancer, and use of photosensitizing drugs.
The treatment process begins with a minimal erythema dose (MED) test to determine your skin's sensitivity. Sessions start at sub-erythemal doses and gradually increase. Typical protocols involve 3 sessions per week for 12 weeks. Maintenance may be weekly or biweekly. Excimer laser sessions are usually shorter and can be performed 2 times per week for 4–6 weeks.
In recent years, home phototherapy devices have become available, but they require proper training and follow-up. Insurance coverage varies, so check your plan. This therapy remains a cornerstone of dermatologic care, offering a safe, effective, and accessible option for millions.
To sum up, whether you choose narrowband UVB, PUVA, or laser, phototherapy can transform your skin and well-being. Always consult a board-certified dermatologist to discuss if UV light treatment is right for you.