Latest news with #photobiology
Yahoo
2 days ago
- Health
- Yahoo
Do I need to wear sunscreen indoors? An expert weighs in
Here's what to know about whether you need to use SPF at home, work, or in the car when sun's streaming through the windows. When the sun's out, most of us know the drill: sunglasses on, SPF applied, and try not to burn. But what about when you're indoors? You might have heard claims that we should be wearing sunscreen every single day – even if we're just working from the sofa or sitting in an office. The logic is that UVA rays – linked to premature ageing and some skin cancers – can pass through glass and still reach your skin. But is this true? Some experts aren't convinced, arguing that the amount of UV you get inside is tiny compared with what you're exposed to outdoors. We asked a professor of photobiology to shed light on whether your indoor SPF habit is helping – or just adding another step to your skincare routine. The SPF-indoors debate Much of the advice about wearing sunscreen inside comes from the fact that UVA rays can pass through glass. There are two main types of ultraviolet radiation from the sun that affect our skin: UVA and UVB. UVA has a longer wavelength, can penetrate through glass, and is present at a consistent level throughout daylight hours. It penetrates deeper into the skin and is linked to skin ageing and, over time, some skin cancers. UVB has a shorter wavelength, is blocked by glass, and is strongest in summer and around midday. It's the main cause of sunburn and plays a key role in vitamin D production. But, Brian Diffey, a professor of photobiology and member of the British Association of Dermatologists, says the amount of daylight your skin gets indoors is affected by a number of variables. These include the season, weather, window size and orientation, the reflectiveness of walls and floors, and outside obstructions like buildings or trees that block direct sunlight. He adds that some dermatologists may give broad guidance about wearing sunscreen indoors because they want to keep people aware of the risks of skin damage and cancer, which is vital, but they're not specialists in the physics of light indoors. "Dermatologists are experts in the diagnosis and treatment of skin disease… you wouldn't expect them to know about the physics of sunlight and the transmission through different materials, and how the geometry of a building affects the light levels inside," he tells Yahoo UK. Do we need to wear sunscreen indoors? According to Professor Diffey, for most people, "there is no need to put sunscreen on indoors." "Light levels indoors are orders of magnitude less than they are outdoors," he says, explaining that in his research, he found spending 10 hours in a well-lit indoor space is roughly equivalent, in terms of UVA exposure, to just 10 minutes outside at midday in summer. He encourages people to think about the amount of sky you can see. "When you're outdoors, the whole sky is visible, and that's where much of the UV comes from," he explains. "Indoors, most of this is blocked by roofs, walls and other buildings." If sunlight does stream directly through a window at home or in the office, Professor Diffey says most people will use common sense and move away or close the blinds because of the glare. "If you've got the window shut, you're going to get no UVB and you're going to get very little UVA, unless you're sitting right next to the window," he adds. The exceptions to SPF indoors While Professor Diffey says most people don't need to use sunscreen indoors, he says there are some groups who may benefit. These include: People with skin diseases that make them very sensitive to light People on drugs like isotretinoin (which thins the skin), or on immunosuppressive therapy Some people in certain jobs, like horticulturalists working in greenhouses He stresses this doesn't mean stopping sunscreen altogether, but rather using it where there's a genuine UV risk – not indoors, where levels are minimal. Can you burn in a car? In cars, Professor Diffey says your skin is 'only seeing a small part of the sky because you've got the roof of the car which blocks it.' He adds that UV becomes more hazardous the higher the sun is in the sky – but when the sun is at its highest point (generally between 11am and 3pm), it's blocked by the car roof. "You only get trouble with sunlight in a car in early morning and late evening if you're driving east or west," he continues. "When the sun is troublesome in the middle of the day, it's unlikely you'll get any direct sunlight coming in the car. And so measurements that I and other people have done show typically, inside a car, you might get about 2% on your skin of what you get outside a car." However, if you have your windows open, you may need sunscreen. "If you're driving along and the sun is coming in through the side window and you've got your window open with your arm exposed, driving for several hours, then you can certainly get a sunburn," he says. When do you really need sunscreen? "Obviously, when you're going to be in strong sunshine for an extended period," you need to use sun lotion, says Professor Diffey. Sunsreen is proven to protect against sunburn – its main purpose – and may help reduce premature ageing and skin cancer risk, so we still need to use it to stay safe in the sun. In the UK, that generally means daily use during the sunnier months, especially if you're spending time outdoors. In winter, when UV levels are much lower, everyday SPF is less essential. Many weather apps, including the Met Office and BBC Weather apps, provide localised UV indexes. 'You don't need to use sunscreen when the UV levels are low, which they are indoors, or in the UK winter," he adds. Read more about suncream: The 4 most important things to check on your sunscreen, according to a dermatologist (Yahoo Life UK, 5-min read) The best sunscreen of 2025 – and the two to avoid (Yahoo Life UK, 5-min read) The 8 best sunscreens for kids and adults – and the correct SPF to use for your age (Yahoo Life UK, 7-min read)
Medscape
08-05-2025
- Health
- Medscape
UK Study Maps Solar Urticaria Features and Treatments
TOPLINE: In a multicentre cross-sectional study, the majority of patients with solar urticaria were of European ethnicity, with Fitzpatrick skin phototypes I-III; urticaria provocation was achieved using monochromator phototesting in 94.2% of participants, and omalizumab showed the highest complete response rate at 37.5%. METHODOLOGY: Researchers conducted a cross-sectional study at six tertiary photobiology units in the United Kingdom between October 2019 and June 2023 and analysed clinical and photobiological features of 178 phototest-positive patients with solar urticaria. Included participants had a diagnosis of solar urticaria done by a consultant photodermatologist and successful urticaria provocation via phototesting. TAKEAWAY: Overall, 67% of participants were women, with a median age of 35 years at disease onset, and the majority self-reported European ethnicity (89.2%), with Fitzpatrick skin phototypes I (16.6%), II (57.3%), and III (14.6%) being most prevalent (88.5%). Urticaria provocation was achieved using monochromator phototesting in 94.2% of participants and using solar simulated radiation in 5.8% of participants. Ultraviolet A (UVA) alone triggered symptoms in 31.3% of patients, UVA combined with visible light affected 29.4% of patients, and UVA with ultraviolet B affected 15.6% of patients. A treatment response analysis revealed that sunscreen and H1-antihistamines were most commonly used (98.2% and 97.6%, respectively), with partial response rates of 61.8% and 69.6%, respectively. Omalizumab demonstrated superior efficacy, with a partial response rate of 53.1% and complete disease control in 37.5% of patients compared with lower complete disease control for other treatments including montelukast (8.5%) and H1-antihistamines (13.5%). IN PRACTICE: "This study describes the clinical presentation of SU [solar urticaria] in 178 individuals and recapitulates several of its characteristics as reported by other investigators. Importantly, it highlights that SU affects individuals of all ethnicities and skin phototypes, although whether ethnicity-specific disease susceptibility exists cannot be ascertained from these data," the authors wrote. SOURCE: This study was led by Navandeep K. Thumber, St John's Institute of Dermatology, London, England. It was published online on April 28, 2025, in the British Journal of Dermatology. LIMITATIONS: This study was limited by the eligibility criteria excluding phototest-negative individuals and the subjective nature of treatment response reporting. DISCLOSURES: This research did not receive any specific grant from any funding agency in the public, commercial, or not-for-profit sectors. The authors reported having no conflicts of interest. This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.
