Phototherapy for Eczema: Types, Efficacy, Risks & Practical Guide

Phototherapy (light therapy) uses controlled ultraviolet (UV) radiation to suppress cutaneous inflammation in moderate-to-severe atopic dermatitis (AD). It is a well-established, steroid-sparing treatment backed by robust evidence.

Mechanism of Action

• Induces apoptosis of activated skin-homing T-cells.
• Reduces pro-inflammatory cytokines (IL-4, IL-13, IL-31, TNF-α).
• Increases regulatory T-cells (Tregs) and IL-10.
• Modulates Langerhans cell function.
• Improves skin barrier by upregulating filaggrin and ceramides.

Types of Phototherapy for AD

Modality	Wavelength	Indication	Pros	Cons
Narrowband UVB (NB-UVB)	311–313 nm	First-line phototherapy for AD	Best efficacy/safety ratio; no psoralen needed; widely available	Requires 2–3 visits/week; cumulative UV dose
Broadband UVB (BB-UVB)	290–320 nm	If NB-UVB unavailable	Older technology	More erythemogenic; less effective
UVA1 (340–400 nm)	340–400 nm	Severe, acute flares; deeper penetration	Penetrates dermis; good for lichenified plaques	Less available; higher photoaging risk
PUVA (Psoralen + UVA)	320–400 nm + psoralen	Refractory AD	Potent	Systemic psoralen side effects (nausea, cataract risk); higher carcinogenicity; complex logistics

Typical NB-UVB Treatment Protocol

• Frequency: 2–3 times per week (non-consecutive days).
• Starting dose: 50–70% of minimal erythema dose (MED) or fixed low dose (0.1–0.3 J/cm²).
• Increment: 10–20% per session if no erythema.
• Duration: 8–12 weeks induction, then maintenance (1×/week to 1×/month) or taper.
• Response: 60–80% achieve ≥50% EASI improvement; itch often improves early.

Risks & Mitigation Strategies

Risk	Mitigation
Erythema (sunburn)	Conservative dosing, patient feedback, dose-hold rules
Photoaging (wrinkles, lentigines)	Limit lifetime sessions; facial shielding; NB-UVB < PUVA
Skin cancer (SCC, BCC, melanoma)	Risk rises with cumulative dose; PUVA > NB-UVB; annual skin checks
Cataracts	UV-blocking goggles mandatory (UVA1, PUVA); recommended for NB-UVB
Herpes simplex reactivation	Prophylactic antiviral if history
Heat exacerbation	Cool cabin, fan, hydration

Ideal Candidates

• Moderate-severe AD (EASI ≥16) inadequately controlled with topicals.
• Unable or unwilling to use systemic immunosuppressants.
• Widespread involvement (impractical for topical therapy).
• Able to adhere to frequent clinic visits.

Insurance & Access

• Covered by most plans (including Medicare/Medicaid) for moderate-severe AD with documented topical failure.
• Requires prior authorization, dermatologist referral, and treatment plan.
• Home NB-UVB units exist (prescription only)—improve adherence but require discipline.

Combination Strategies

• Phototherapy + topical maintenance therapy.
• Phototherapy as a bridge to biologic or JAK inhibitor.
• Phototherapy + dupilumab (emerging data suggest synergy, may allow phototherapy taper).

Phototherapy is a high-value, non-systemic option for AD. NB-UVB is the workhorse. Success requires partnership: a skilled phototherapy unit, an engaged patient, and an overseeing dermatologist.