Experts Urge Indoor Sunscreen as 99% UV-Blocking Films Cut Window Exposure

Q: Your window blocks sunburn, but how much invisible 'aging radiation' is it letting through to damage your skin daily?

A standard window may block the rays that cause sunburn, but it can still let through a large share of the “aging” rays: typically about 25% to 75% of UVA, and in some common clear or tempered glass, around 70%. That matters because UVA penetrates deeper into skin than UVB. It does not usually cause the immediate warning sign of sunburn, but it is strongly linked to cumulative damage such as wrinkles, loss of firmness, dark spots, uneven pigmentation and, over time, higher skin cancer risk. Dermatologists cited in the report stress that being indoors does not stop this exposure if you sit near daylight through glass. Research supports the concern. Standard residential and office glass blocks most UVB, but not most UVA. Experts note that repeated UVA exposure through windows can produce visible photoaging, including asymmetrical aging on the side of the face or body closest to a window. People using retinoids, AHAs or other sun-sensitizing treatments are especially vulnerable. Protection is practical. Broad-spectrum SPF 30 or higher remains the main recommendation, even indoors if you spend hours near windows. Moving farther from the glass, closing blinds during peak daylight, and choosing north-facing or less sun-exposed rooms can reduce exposure. For stronger protection, UV-blocking window films can block more than 99% of UVA and UVB, while laminated or low-E glass can sharply cut UVA transmission, in some cases close to zero.

3 articles · Updated · Hindustan Times · Jun 16

Dermatologists and skincare experts say sunscreen should remain a daily habit indoors, especially for people who sit for hours near windows, drive often or work in bright offices.
UVA rays can pass through standard glass even though most UVB is blocked, exposing skin to pigmentation, uneven tone and premature ageing over time.
Blue light from long-term screen use may also add to pigmentation, and experts say indoor protection matters even more for people using retinoids, AHAs or BHAs, or treating melasma and acne marks.
Practical steps include sitting farther from direct sunlight, closing blinds from 10 a.m. to 4 p.m., using protective clothing, and installing clear window films that block 99% or more of UVA and UVB.