Do You Need Sunscreen in Winter? Plus the First New US Filter in Over 25 Years

Winter sunscreen earns its place on the days that involve glass, snow or altitude. UVB drops sharply as the sun sits lower, so sunburn risk falls with it, but UVA keeps arriving all year and passes through window glass. Fresh snow reflects as much as 80% of UV, which can double a ski day's exposure.

So Do You Need Sunscreen in Winter, or Not?

Key Takeaways

UVA reaches the ground year round and comes through window glass; UVB, the band that burns, falls hard as the sun sits lower ⁵⁶.

WHO puts the protection threshold at a UV index of 3, and plenty of temperate winter days sit below it away from snow and altitude ⁵.

Fresh snow reflects as much as 80% of UV, and every 1,000 meters of altitude adds 10% to 12% ⁵.

Front windshields blocked 96% of UVA on average in a 29-car study; driver's side windows managed 71% ⁸.

The FDA added bemotrizinol to the US list of permitted sunscreen filters at up to 6%, effective 9 August 2026, the first addition since the late 1990s ¹².

Sunlight loses most of its UVB on the way down. The atmosphere absorbs roughly 90% of it, so what reaches you in December is largely UVA with a small UVB component ⁵. Sun elevation does the rest: the lower the sun sits, the less UV arrives ⁵.

WHO's own guidance stops short of sunscreen everywhere, every day. Below a UV index of 3, it says the risk is limited and no protective measures are normally needed ⁵. Above 3, protection becomes necessary.

That threshold is worth knowing, because the UV index tracks sunburn risk, and sunburn is not the only thing UV does to skin.

Does UVA Really Come Through Window Glass?

Ask a skincare forum whether SPF matters indoors and the top-voted reply is usually a flat no. Glass makes that half right: every common type of window and automobile glass blocks the majority of UVB, while some of the longer UVA still comes through, and how much depends on the type of glass. Laminated glass performs better than tempered ⁶⁷.

Cars make the difference measurable. Across 29 cars from 15 manufacturers, front windshields blocked 96% of UVA on average, while driver's side windows blocked 71%, ranging from 44% to 96% ⁸. Windshields are laminated. Side windows usually are not, which is why a long commute is a one-sided exposure.

Winter does slow UVA down. Measured across a year, the minimum time for UVA alone to deliver one standard erythemal dose, the unit researchers use for skin-reddening UV, runs roughly 2× longer in winter than in summer ⁶. Slower still adds up over a season of eight-hour desk days.

If you sit beside a bright window or drive into a low winter sun, sunscreen is doing something even with frost on the ground. We made the broader case for daily SPF in do you need sunscreen every day.

Who Needs Winter Sunscreen Most?

Pigmentation-prone skin. Melasma and the dark marks left by spots respond to exposure that never comes near a sunburn. Sunscreen use supports protection against pigmentary disorders as well as sunburn and photoaging ⁹, and winter is when people relax the habit that kept those marks quiet all summer. If melasma is not shifting, that is a conversation for a dermatologist.

Retinoid and acid users. In FDA's study, four weeks of alpha hydroxy acid use raised sensitivity to UV reddening by 18%, and the agency recommends AHA products carry a sunburn alert ¹⁰. Retinoid users belong in the same group, because skin adjusting to a retinoid can be more reactive to UV. If your evening routine contains actives, morning SPF is part of that routine rather than a seasonal extra. Patch test anything new on your inner arm, add one product at a time, and keep the SPF step in daylight hours.

Anyone on snow or at altitude. Fresh snow reflects as much as 80% of UV, reflection can double your overall exposure, and each 1,000 meters of altitude adds 10% to 12% more UV ⁵.

Window-seat workers and drivers. Hours of low-level UVA through glass, five days a week, all winter ⁶⁸.

Which Winter Days Actually Need SPF?

No sunscreen is 100%, whichever filters are in it. On exposed days, reapply every two hours and let shade, a hat and clothing carry part of the load ⁵. If a sunscreen makes your winter skin feel tight or dry, an SPF moisturizer combo can be an easier daily step than a second layer. If white cast is the reason you skip it, tinted formulas are worth a try.

What Is Bemotrizinol, and What Did the FDA Approve?

Bemotrizinol is an organic UV filter that absorbs across both UVA and UVB ², and it is photostable: it holds its filtering power under light instead of degrading through the day. Lab work on the filter, sold in Europe as Tinosorb S, found it also slowed the breakdown of avobenzone, the long-UVA filter US sunscreens lean on, keeping a formula's SPF and UVA protection steady through heavy irradiation ⁴.

On 9 June 2026 the FDA announced a final order adding bemotrizinol to the over-the-counter sunscreen monograph, the rulebook that sets which filters US sunscreens may use, at concentrations up to 6% ¹². It is the first new active ingredient added to that monograph since the late 1990s ², and the order takes effect on 9 August 2026 ¹.

FDA concluded the filter is safe and effective for adults and children 6 months and older at up to 6%. Its review reported that bemotrizinol is not readily absorbed through human skin even with repeat application, and that the skin studies turned up no irritation and no reactions triggered by sunlight on treated skin ¹.

Europe reached a similar conclusion a generation earlier. Commission Directive 2000/6/EC added bemotrizinol to the EU's permitted UV filter list in 2000 at up to 10% ³.

What Changes for US Shoppers, and What Does Not?

Very little this winter. DSM, which filed the request, holds 18 months of exclusivity from the effective date ¹, so US formulas using bemotrizinol will trickle in rather than arrive all at once.

The monograph list got one ingredient longer. Bemotrizinol may be combined with other permitted filters apart from aminobenzoic acid and trolamine salicylate, in oils, lotions, creams, gels, butters, pastes, ointments and sticks. Sprays count only where the propellant never touches the formula, which means pump bottles and bag-on-valve systems; FDA refused propellant-based aerosol cans on the data submitted, and powders were left off too, though other filters keep both ¹. Every product still has to pass the same SPF and broad-spectrum tests behind the label ¹.

The question we get at Skin Bliss is whether to wait. Your current sunscreen does not expire on 9 August 2026, and the one you will actually reapply beats a better filter you leave in the drawer. If you are choosing now, mineral versus chemical is the more useful comparison.

Use This in Your Routine

Skin Bliss is a skincare scanner that checks whether products actually fit your skin, before you buy. Two parts of the app fit a winter SPF question specifically.

Ingredient List Analyzer reads the filter list of any sunscreen, including one you photographed on a trip to Europe, so you can see which filters are carrying the UVA load in the bottle you already own. Weather-Based Skincare Alerts respond to local humidity, temperature and wind, which is usually what breaks a winter routine: skin feels tight in the cold, and the morning SPF step is the first one to go.

You can start at getskinbliss.com.

Save this one for the first bright January morning, when the question comes back around.

FAQ

Do you need sunscreen indoors in winter?

Only where windows are involved. Ordinary glass blocks most UVB and lets some UVA through, so a desk in daylight is a real low-level exposure while a windowless room is not ⁶⁷. If you sit in bright daylight for hours, morning SPF on face and hands covers it. If you do not, skipping it costs you nothing.

Is SPF 30 enough for a winter day?

For an ordinary temperate winter day, yes, applied properly to face, ears and hands. On snow or at altitude, move up to SPF 50 and reapply, because reflection can double your exposure and every 1,000 meters adds 10% to 12% more UV ⁵. No sunscreen is 100%, so reapply every two hours of real exposure.

Can you get sunburned on a ski day?

Yes, easily. Fresh snow reflects as much as 80% of UV, so the dose arrives from above and below at once, and altitude adds 10% to 12% per 1,000 meters climbed ⁵. Cold air masks the usual warning signs. Cover the underside of your chin and nose, and do not skip SPF lip balm.

When will US sunscreens contain bemotrizinol?

The order takes effect on 9 August 2026, and DSM holds 18 months of exclusivity from that date ¹. Expect a slow trickle of reformulated products rather than a shelf full of new options this winter. Sunscreens sold in Europe have contained the filter since 2000, so a bottle bought on a trip is one way to try it early.

Is bemotrizinol the same thing as Tinosorb S?

Same molecule, different naming systems. Bemotrizinol is the name FDA uses in the monograph, Tinosorb S is BASF's trade name, and the ingredient list name is bis-ethylhexyloxyphenol methoxyphenyl triazine ⁴. Bisoctrizole, sold as Tinosorb M, is a separate filter and is not part of this order ¹.