NB-UVB Side Effects
Narrowband UVB phototherapy causes short-term side effects including skin redness, discomfort, and potential heat intolerance in the light box, while long-term risks include accelerated skin aging and increased nonmelanoma skin cancer risk, though notably there is no evidence for a specific increase in skin cancer after NB-UVB compared to other UV exposures. 1
Short-Term Side Effects
The acute side effects are generally mild and manageable:
- Erythema (skin redness): Most common acute effect, occurring in 10-94% of patients depending on treatment regimen 2. In recent studies, erythema was reported in 12.5% of patients 3 and was well-tolerated in most cases 4
- Discomfort and burning sensation: Reported in approximately 60% of patients 5, though typically mild
- Pruritus (itching): Common but may reflect underlying disease rather than phototherapy itself 2
- Heat-related symptoms: Feeling faint in the light box due to heat generation during treatment 1. Patients with heat intolerance, heart disease, or claustrophobia require special consideration before initiating therapy
- Blistering: Rare but documented, particularly of psoriatic plaques mid-treatment course 2
- Herpes simplex reactivation: Occasionally reported 6
- Pain: Documented in geriatric populations 4
Long-Term Side Effects
Photoaging
Long-term NB-UVB accelerates skin aging similar to excessive sun damage, resulting in increased wrinkling 1. This occurs through reduced dermal hydroxyproline levels and induction of gelatinases and elastin cross-links 2.
Pigmentation Changes
Skin Cancer Risk
Critical nuance: While repetitive UV exposure increases nonmelanoma skin cancer risk (squamous cell carcinoma and basal cell carcinoma), there is no evidence for a specific increase after NB-UVB 1.
The evidence shows:
- Animal models suggest NB-UVB may be 2-3 times more carcinogenic per minimal erythema dose (MED) than broadband UVB 2, 7
- However, because NB-UVB requires far fewer total MEDs to achieve clearance, the cumulative carcinogenic risk may actually be lower than broadband UVB 7
- A large review of 3,867 patients (median 29 treatments, 352 patients receiving >100 treatments) found no significant association with basal cell carcinoma, squamous cell carcinoma, or melanoma over a median 5.5-year follow-up 7
- Most studies have not found increased risk of melanoma or nonmelanoma skin cancer with NB-UVB 8
Monitoring requirement: All patients treated with UV light should undergo yearly skin examinations for early detection of new skin cancers, as skin cancer remains a delayed risk 1
Special Population Considerations
Pediatric Patients
- Well-tolerated in children aged 4-16 years 6, 9
- Adverse event profile similar to adults
- Anxiety was problematic in 5 patients in one series 6
- Acute side effects occurred in only 14.3% of pediatric patients 9
Geriatric Patients
- Safe and effective in patients ≥60 years 4
- Side effects experienced by 30% (pain, burn, itch)
- Most side effects mild and did not require discontinuation 4
Pregnancy
Pregnancy is not a contraindication to NB-UVB therapy and should be considered first-line for pregnant patients requiring systemic treatment 7
Common Pitfalls to Avoid
Sunscreen application on treatment days: Do not apply sunscreen before NB-UVB exposure, as this creates areas of differential tolerance and can cause burning on subsequent sessions 1
Inadequate genital shielding: Men must shield genitals with athletic supporter or sock; women should shield nipples with SPF 50 sunscreen or zinc oxide 1
Concurrent sun exposure: No sun tanning or tanning beds during NB-UVB treatment, as this affects UV dose received and increases skin cancer risk 1
Missing dose adjustments: Report any redness or discomfort before each treatment to allow proper dose calculation 1
Inadequate follow-up: Regular dermatologic evaluation during treatment and annual skin examinations are mandatory 1