What SPF and PA actually mean, how much to apply, how often to reapply, and why cooling temperatures and mountain air don't let you off the hook.
Most of us know we should wear sunscreen. Fewer of us know what the numbers on the bottle mean, how much to apply, or whether it's actually necessary on a grey day in Zurich in November.
These aren't small details. Sunscreen only works when it's understood and used correctly, and that gap is where most sun protection quietly fails. Here's the complete guide.
What do SPF and PA actually mean?
SPF (Sun Protection Factor) measures protection against UVB rays, the ones mainly responsible for sunburn. SPF50 doesn't mean you're protected 50 times longer in a literal sense, but it does mean a much smaller fraction of UVB reaches your skin compared to no protection at all. In practical terms, higher SPF gives you a wider safety margin, which matters since most people apply less than the tested amount anyway.
PA (Protection Grade of UVA) measures protection against UVA rays, the ones linked to premature ageing and deeper skin damage. It's graded in plus signs, from PA+ up to PA++++, the more pluses, the stronger the UVA protection. A good daily sunscreen covers both: a solid SPF number for UVB, and a strong PA rating for UVA. One without the other only tells half the story.
How much sunscreen should I actually apply?
A thin layer isn't enough. For optimal UV protection on the face, dermatologists generally recommend applying about two finger lengths' worth, more than most people instinctively use. Using less than this significantly lowers the actual protection you get, no matter what SPF or PA number is printed on the bottle.
Do I really need to reapply?
Yes. Sunscreen breaks down over time, from sweat, from touching your face, from simply being out in the sun. Reapplying every 2 to 3 hours keeps protection at an effective level, and this matters even more during outdoor activities or in high heat and humidity, when sunscreen wears off faster than you'd expect.
Do I need sunscreen indoors or on cloudy days?
Yes, and this is the one that surprises people most. UVA rays pass through both glass and clouds. Sitting near a window or heading out on an overcast day doesn't mean you're protected. Daily sunscreen use is recommended regardless of the weather or where you are, indoors included.
Can I skip sunscreen once the weather cools down?
This is probably the most common myth of all. UVA rays are present year round, regardless of temperature or season. As autumn sets in and the days feel cooler, it's tempting to file sunscreen away with your summer clothes, but UV exposure doesn't follow the thermometer. A crisp, cold, sunny day can expose your skin to just as much UVA as a warm one.
Does altitude really make a difference?
Yes, and for anyone living in or visiting Switzerland, this one matters more than most places. UV exposure increases with altitude, the higher you go, the less atmosphere there is to filter it. Spend a day up in the mountains and your skin is exposed to meaningfully more UV than the same day at sea level, even if the air feels colder.
Snow adds another layer to this. It reflects a large portion of UV radiation back up at your face, which is exactly why skiers and hikers can get sunburned on a cold, overcast day on the slopes. If you're heading up to the Alps this autumn or winter, sunscreen belongs in your bag right next to your gloves, not just in your summer packing list.
Do I need to cleanse it off properly at night?
Yes, this step gets overlooked more than any other. Higher SPF and water resistant formulas are built to stay put through sweat, water, and touch, which is exactly why a quick rinse or a single micellar wipe often isn't enough to fully remove them. Leftover sunscreen sitting on the skin overnight can clog pores and contribute to breakouts or irritation over time. A simple fix is double cleansing in the evening: an oil or balm based cleanser first to break down sunscreen and sebum, followed by your regular water based cleanser to finish. It only takes an extra minute, and it's what actually lets your skin recover overnight instead of carrying the day's sunscreen into your pillow.
The right SPF, whatever the season
Two Banobagi sunscreens, for every day of the year
At KESSENTIAL, we curate products formulated with clinically tested actives, not passing trends. Here are two Banobagi sunscreens worth knowing about, one available now, one landing soon.
And if you need something for quick reapplication on the go, keep an eye out, a matte, oil-control Sun Stick is joining the lineup soon.
After matters just as much as before
Good sun protection doesn't end when you take your sunscreen off. Properly cleansing it away at night, and giving your skin something to recover with, matters just as much as applying it correctly in the morning. Banobagi's Milk Thistle Repair line is built for exactly this, a gentle cleanser to fully remove sunscreen and daily buildup, and a soothing mask to help calm and replenish skin after a day of sun exposure.
Explore the Milk Thistle Repair line, shipped locally and directly from Switzerland.
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