308nm UVB Phototherapy at Home — Complete FAQ

This page answers the most common clinical and practical questions about 308nm targeted UVB phototherapy, including at-home use with FDA-cleared devices like Tendly Light. Questions are organized by topic. Answers reflect published clinical literature and standard dermatology practice.

About 308nm UVB Phototherapy

What is 308nm UVB phototherapy?

308nm UVB phototherapy is a form of targeted ultraviolet B light therapy that delivers a specific wavelength — 308 nanometers — directly to affected skin. It is used clinically to treat vitiligo, psoriasis, and eczema (atopic dermatitis). The 308nm wavelength was identified through clinical research as the most therapeutically effective UVB wavelength for stimulating melanocyte activity (in vitiligo) and suppressing inflammatory skin responses (in psoriasis and eczema).

Why specifically 308nm and not other UV wavelengths?

Different UV wavelengths have different biological effects on skin. Broadband UVB (280–320nm) covers a wide range including wavelengths that cause sunburn without meaningful therapeutic benefit. Narrowband UVB at 311–313nm (used in full-body panels) was a significant improvement. 308nm specifically emerged from studies showing it stimulates melanocyte migration and proliferation more efficiently than adjacent wavelengths, while targeted delivery (as opposed to whole-body exposure) further reduces cumulative UV load on healthy skin.

What conditions does 308nm UVB treat?

• Vitiligo: Stimulates repigmentation by activating residual melanocytes at patch borders and prompting new melanocyte migration from hair follicles.
• Psoriasis (plaque): Reduces keratinocyte proliferation and inflammatory T-cell activity driving plaque formation. Particularly effective for localized plaques on elbows, knees, and scalp.
• Atopic dermatitis (eczema): Suppresses local inflammatory mediators, reducing lesion severity, itch, and skin barrier disruption.

Is 308nm phototherapy the same as sunlight?

No. Sunlight contains a broad spectrum of UV wavelengths (UVA 315–400nm, UVB 280–315nm) plus visible and infrared light. Most of the UV in sunlight is UVA, which has limited therapeutic value for vitiligo and psoriasis but contributes significantly to skin aging and DNA damage. 308nm targeted devices isolate the single most therapeutically relevant wavelength and apply it only to the affected area, minimizing off-target exposure.

At-Home Use

Can I use 308nm UVB therapy at home?

Yes — FDA 510(k)-cleared 308nm LED devices are approved for home use by adults. The FDA's 510(k) pathway evaluates the device against a predicate (a previously cleared clinical device) for safety and efficacy. Cleared home devices are held to the same therapeutic wavelength standard as clinical devices, though typically at lower intensity (mW/cm²) than excimer lasers used in clinics. Tendly Light is FDA 510(k) cleared for home use for vitiligo, psoriasis, and eczema.

Do I need a prescription for a home 308nm UVB device?

No prescription is required to purchase FDA-cleared 308nm home devices in the United States. However, consulting your dermatologist before starting is strongly recommended — particularly to establish a starting dose, identify any contraindications (photosensitizing medications, personal history of skin cancer), and confirm that phototherapy is appropriate for your specific condition and skin type.

How effective is at-home 308nm UVB compared to clinic treatment?

The primary difference between clinic and home 308nm devices is intensity. Clinic excimer lasers typically deliver 50–150 mW/cm², while home LED devices deliver 15–25 mW/cm². This means individual sessions take longer at home to reach the same dose in J/cm². However, clinical research on at-home narrowband UVB devices has shown that consistent treatment frequency (3–5 sessions per week) produces comparable cumulative outcomes over a course of weeks. The most significant advantage of home treatment is adherence — patients who own a device treat far more consistently than those who must schedule clinic appointments 2–3 times weekly.

How long does treatment take before I see results?

• Vitiligo: Initial repigmentation signals (small dots of color appearing at patch borders) typically appear at 8–12 weeks of consistent 3–5× weekly treatment. Meaningful repigmentation is usually visible at 16–24 weeks. Acral locations (hands, feet) respond more slowly than facial and neck patches.
• Psoriasis: Plaque thinning and lesion reduction typically begin at 4–8 weeks with 3× weekly sessions. Significant clearance is often achieved at 8–12 weeks.
• Eczema: Itch reduction and lesion improvement generally begin at 4–8 weeks. Persistent localized patches that have not responded to topicals often show meaningful improvement by week 8–10.

How often should I treat?

Standard clinical protocols recommend 3–5 sessions per week, with at least one day between sessions. Daily treatment of the same area is not recommended — skin needs recovery time to respond appropriately and signal-dose escalation. Most published protocols target 3× weekly as the minimum effective frequency.

Dosing and Safety

What dose should I start at?

Starting dose depends on your Fitzpatrick skin type and the sensitivity of the treatment area. General starting guidelines:

• Fitzpatrick I–II (very fair to fair skin): 0.05–0.07 J/cm²
• Fitzpatrick III–IV (medium to olive skin): 0.10–0.12 J/cm²
• Fitzpatrick V–VI (brown to dark skin): 0.12–0.18 J/cm²
• Sensitive areas (face, lips, eyelids, groin, underarms): reduce by 40–50% regardless of skin type

Always begin at the lowest appropriate dose and increase by one increment (typically 0.05 J/cm²) every 3–5 sessions if no lasting erythema appears within 24 hours of treatment.

How do I know if my dose is too high?

Check the treated area 6–10 hours after each session, not immediately after. Signs to watch for:

• Acceptable: Mild warmth or very faint pink that resolves within 24 hours.
• Hold dose: Redness that persists beyond 24 hours — do not increase dose next session, treat at same level.
• Reduce dose: Redness that persists beyond 48 hours — drop one dose increment next session.
• Stop and consult dermatologist: Blistering, persistent pain, swelling, or any reaction lasting more than 72 hours.

Is 308nm UVB safe long-term?

Targeted 308nm UVB has a significantly better long-term safety profile than broadband UV or sun exposure because only the affected patch area receives UV energy. Clinical use of narrowband and targeted UVB phototherapy over decades has not demonstrated elevated rates of skin cancer versus the general population in published literature. As with all UV exposure, cumulative dose should be tracked over a treatment course. Patients with a personal or family history of skin cancer should consult a dermatologist before starting.

What medications interact with UVB phototherapy?

Several medication classes increase photosensitivity and may require dose adjustment or avoidance of phototherapy:

• Certain antibiotics (tetracyclines, fluoroquinolones, sulfonamides)
• Diuretics (thiazides, furosemide)
• NSAIDs (ibuprofen, naproxen, particularly at high doses)
• Retinoids (isotretinoin, tretinoin — significantly increase photosensitivity)
• Psoralens (used in PUVA therapy — do not combine with home devices)
• Certain antidepressants and antipsychotics

Always review your current medications with your prescribing physician or pharmacist before starting phototherapy.

Vitiligo-Specific Questions

Why does 308nm UVB work for vitiligo?

Vitiligo results from the immune-mediated destruction of melanocytes — cells that produce skin pigment (melanin). 308nm UVB works through two mechanisms: (1) it suppresses the local autoimmune activity that continues to destroy melanocytes, and (2) it stimulates the migration and proliferation of residual melanocytes from hair follicles into depigmented patches. The result, over weeks of consistent treatment, is the gradual return of pigmentation from the patch edges inward.

Which vitiligo patches respond best?

Response to 308nm phototherapy varies significantly by location. Face and neck patches typically show the fastest and most complete response. Trunk and proximal limb patches respond moderately well. Acral patches (hands, feet, fingers, toes) and patches over bony prominences respond most slowly and least completely. Patches with white hair within them (leukotrichia) are particularly resistant, as this indicates loss of the follicular melanocyte reservoir that drives repigmentation.

Can 308nm UVB cure vitiligo?

308nm phototherapy does not cure vitiligo — it does not correct the underlying autoimmune mechanism that causes melanocyte destruction. However, it can achieve meaningful to near-complete repigmentation of treated patches over a treatment course of months. Maintenance treatment (reduced frequency) is often required to sustain results. Some patients experience stable long-term repigmentation; others see gradual re-depigmentation if treatment is stopped.

Psoriasis-Specific Questions

How does 308nm UVB compare to biologics for psoriasis?

308nm phototherapy and biologics (adalimumab, ixekizumab, secukinumab, etc.) target different aspects of the psoriasis immune cascade and are not directly comparable as systemic versus localized treatments. Biologics affect whole-body immune activity and are particularly suited to widespread or systemic psoriasis. Targeted 308nm UVB is most appropriate for localized plaque psoriasis — well-defined plaques on elbows, knees, scalp, and hands — where systemic immunosuppression may be disproportionate to the disease burden. Many dermatologists use targeted phototherapy alongside or instead of topical steroids for localized disease, reserving biologics for moderate-to-severe widespread disease.

Can I use 308nm UVB if I'm already on a biologic?

Generally yes — targeted phototherapy is not contraindicated with biologic therapy and some dermatologists use them in combination for enhanced outcomes. Consult your prescribing dermatologist before combining treatments.

Medical disclaimer: This page is for informational purposes only and does not constitute medical advice. Always consult a qualified dermatologist before starting phototherapy.

Learn about Tendly Light — FDA 510(k) Cleared 308nm Home Device →