SPF 50 blocks 98% of the harmful UVB rays, and it allows your skin to resist to sunburn 50 times longer than if it was unprotected. However, this doesn’t mean that you should stay in the sun all day. It doesn’t matter how often you swim, towel off your skin or sweat – as a general rule with all SPF levels, you should reapply your sunscreen every two hours or get out of the sun altogether.

You may think that since you live in a colder climate, it’s cloudy outside or you’re spending the day indoors, you don’t need to protect your skin. But you do! UVA, UVB and visible light can still reach your skin even when it’s overcast. Sunlight can reflect on shiny surfaces and penetrate through windows, reaching the deeper layers of your skin even when you can’t see it.

Most people apply a way too small amount of sunscreen. You need around two tablespoons of sunscreen to cover your whole body, and if you are using a spray, it can be difficult to guarantee that you are covering every spot. To be on the safe side, make sure you see a substantial layer of moisture on your skin before rubbing it in, and as always, be diligent with reapplication.

If you don’t use sunscreen as part of your morning skincare routine, maybe you are one of the people who only apply sunscreen when already on the beach. Fact is, you should be applying sunscreen 15-20 minutes before exposing your skin to sunlight for the sunscreen to work optimally, and if you apply it when already on the beach you risk leaving your skin exposed to sunburn.

SPF protects your skin from UVB damage, which is responsible for sunburn, but you need broad-spectrum filters to protect your skin from both UVB and UVB rays. UVA are considered the most damaging, because they can penetrate the skin more deeply and cause premature ageing and skin cancer. For the most effective protection from damaging rays, choose a sunscreen with both a high SPF and broad-spectrum UV filters that provide both a high SPF and UVA protection.