"Does the sun help eczema" is really three questions wearing one coat. A summer afternoon is unmeasured exposure, packaged with warm weather and the chance of burning. A supervised narrowband UVB course is dosed per session in a hospital department, and it is a real treatment, though with less evidence than most people assume. And a minority of people have eczema that sunlight provokes rather than settles, sometimes because of a drug they are already using.
Nothing on the NHS page for treating atopic eczema mentions phototherapy, light treatment or UV. It names emollients, topical corticosteroids and dressings, then says a GP "can prescribe some treatments, or you may be referred to a skin specialist (dermatologist)" (NHS, Atopic eczema treatment). The hospital option surfaces at an appointment or not at all.
An afternoon outdoors is not a dose of phototherapy
UV suppresses immune activity in the skin, which is why a controlled dose is used as a treatment. The cellular detail sits in the companion post on sunscreen for eczema-prone skin, which also covers filter choice and how much to apply.
A hospital course controls dose per session, the interval between sessions and the total. Weather controls none of those. The British Association of Dermatologists puts light treatment under "other treatments", after topical and oral or injected options, and is direct about the shortcut: "Some people affected by chronic eczema benefit from ultraviolet light treatment. This is usually given in a specialist hospital department. This is not usually recommended for children. Commercial sunbeds should not be used to treat eczema" (BAD, Atopic eczema).
Photoaggravated eczema, and why it takes years to spot
Sunlight makes some people's eczema worse, and the pattern is easy to miss because it looks like ordinary eczema. Photoaggravated atopic dermatitis "is estimated to affect between 1.4% and 16% of people with AD" (Rutter et al, 2022).
A Manchester photobiology unit characterised 120 consecutive cases: of 869 patients who underwent photoinvestigation, 14% were diagnosed with the condition. Most, 62 of 104, presented with sunlight-provoked or photodistributed eczema. Seasonally worse eczema was a presenting feature in 50 (48%) and photodistributed eczema in 45 (43%). Median age at onset of photosensitivity was 37 years (range 1 to 72), and median age at diagnosis was 45, eight years later.
Provocation of rash through window glass was reported by 42 of the 89 patients with data on that question (47%), so a desk by a window can be the exposure, not a beach. Formal testing then splits in two. Broadband UV provocation was positive for 112 patients (93%), while monochromator phototesting, which measures the threshold for redness in narrow wavebands, was abnormal for only 28 (23%). Sensitivity that provocation exposes need not show up as a lowered burn threshold.
If your skin worsens in a repeating seasonal pattern, a dated trigger log covering sun exposure and hours outdoors is the most useful thing to take to an appointment. The eight years between median onset and median diagnosis is what happens when the pattern lives in memory rather than on paper.
What the Cochrane review actually found
Musters and colleagues reviewed phototherapy for atopic eczema for Cochrane in 2021, including 32 trials with 1219 randomised participants across all comparisons (Musters et al, 2021). The headline finding is narrower than that total suggests.
Compared with placebo or no treatment, narrowband UVB reduced physician-assessed signs by a mean difference of 9.4 points on a 0 to 90 scale after 12 weeks, with a confidence interval running from 15.18 to 3.62 lower. Patient-reported itch improvement had a risk ratio of 1.72 (1.10 to 2.69), and global improvement rated moderate or better a risk ratio of 2.81 (1.10 to 7.17). Each estimate comes from a single trial of about 40 people: 41, 40 and 41 participants. The review graded them "low-certainty evidence, due to risk of bias and imprecision", so the true effect may sit some way from the number.
Comparisons between phototherapy types are weaker. Narrowband UVB against UVA1, and narrowband UVB against PUVA, were both rated very low certainty for all reported outcomes. There is no dependable basis for saying one lamp beats another.
Withdrawal due to adverse events may not differ either, on three trials and 89 participants. The reported events were "low rates of phototoxic reaction, severe irritation, UV burn, bacterial superinfection, disease exacerbation, and eczema herpeticum". The authors' conclusion is deliberately hedged: narrowband UVB "may improve physician-rated signs, patient-reported symptoms, and IGA after 12 weeks".
What a course actually involves
Treatments "are generally given 2-3 times a week for 12-16 weeks", each session up to 10 minutes in the machine, with protective goggles and genital protection for male patients (BAD, Phototherapy). Most patients improve after about 30 treatments and stay settled for three to four months or longer, though the leaflet is careful to add that this varies from one patient to another and from one skin disease to another. It is not curative and may need repeating.
Side effects during a course include mild sunburn reactions, dry and itchy skin, skin darkening, prickly heat rash in about 1 in 10 people, and cold sores in about 1 in 30. The longer-term arithmetic is stated plainly on the same leaflet: a course every year across a whole lifetime would in general double the risk of treatable skin cancer, and it is usual practice to be reviewed for skin cancer once you have had more than 500 UVB treatments.
Two or three hospital visits a week for three months is a real demand on work and travel, and often what decides whether a course gets finished.
Where phototherapy sits in NHS care
NICE places it above topical treatment, not alongside it. The guideline for children under 12 says: "Consider phototherapy or systemic treatments for severe atopic eczema in children when other management options have failed or are inappropriate, and there is a significant negative impact on quality of life. Only use phototherapy and systemic treatments under specialist dermatological supervision by staff who are experienced in working with children" (NICE CG57, 1.5.1.43).
There is a gate before it starts. Recommendation 1.5.1.44 says to "Only start phototherapy or systemic treatments in children with atopic eczema after assessment and documentation of severity of atopic eczema and quality of life". CG57 covers under-12s, while the BAD leaflet says light treatment is not usually recommended for children, so this is a decision a dermatologist makes case by case. The route to that appointment, and what else secondary care can offer, is set out in when to see a dermatologist about eczema.
Treatments that change how your skin handles UV
Some eczema treatments alter sun tolerance directly. The summary of product characteristics for Protopic 0.1% ointment states that "Exposure of the skin to sunlight should be minimised and the use of ultraviolet (UV) light from a solarium, therapy with UVB or UVA in combination with psoralens (PUVA) should be avoided during use of Protopic ointment" (Protopic SmPC). The BAD leaflet makes the same point about the class: topical calcineurin inhibitors "can make your skin more sensitive to sunlight" (BAD, Atopic eczema), with daytime sun protection advised; which product suits is covered in the sunscreen post.
This is the one part of the topic worth raising with the person who prescribed the treatment rather than resolving from an article.
Through the year
Summer and winter fail eczema-prone skin in opposite directions. Winter flares run on low humidity, heating and hot showers, covered in why cold weather makes eczema worse. Summer adds heat and sweat to skin that may or may not be getting any benefit from the light. The photoaggravated figures above are the reason to check whether it helps your own skin rather than assume.
References
- NHS. Atopic eczema: treatment. https://www.nhs.uk/conditions/atopic-eczema/treatment/
- National Institute for Health and Care Excellence. Atopic eczema in under 12s: diagnosis and management (CG57), 2025. https://www.ncbi.nlm.nih.gov/books/NBK571009/
- British Association of Dermatologists. Atopic eczema, patient information leaflet. https://www.bad.org.uk/pils/atopic-eczema/
- British Association of Dermatologists. Phototherapy, patient information. https://www.skinhealthinfo.org.uk/condition/phototherapy/
- Musters AH, Mashayekhi S, Harvey J, et al. Phototherapy for atopic eczema. Cochrane Database of Systematic Reviews, 2021. DOI 10.1002/14651858.CD013870.pub2. https://pmc.ncbi.nlm.nih.gov/articles/PMC8552896/
- Rutter KJ, Farrar MD, Marjanovic EJ, Rhodes LE. Clinicophotobiological characterization of photoaggravated atopic dermatitis. JAMA Dermatology, 2022. https://pmc.ncbi.nlm.nih.gov/articles/PMC9330275/
- Electronic Medicines Compendium. Protopic 0.1% ointment, summary of product characteristics. https://www.medicines.org.uk/emc/product/1608/smpc