Guide

Can you simply add up the sun protection factor from two products?

25-6-2025

Translation: Elicia Payne

30 + 50 equals 80, right? When it comes to sun protection factor, however, the math doesn’t add up. There are some advantages to mixing sun protection, but not in the way you might think.

Ever wondered whether you can achieve a higher sun protection factor (SPF) by layering several sun protection products? This idea may not sound so far-fetched to many, but it’s still wrong, as Joëlle Jufer from the Swiss Cancer League explains to me: «If you apply two products with different sun protection factors on top of each other – for example a cream with SPF 50+ then a spray with SPF 30 – you can’t assume a higher level of protection than a maximum of 50+. And that’s assuming you’ve applied cream thoroughly and generously.»

However, combining several products isn’t completely pointless, says the prevention expert. «Most people use too little sunscreen. If you apply cream or spray a second time, you’re more likely to have applied enough product and may catch areas that you missed the first time.»

Sun protection products protect our skin from ultraviolet radiation. This comes from sunlight and isn’t visible to the eye. Two types of UV radiation are particularly relevant in this context: UVA and UVB. The abbreviation SPF (sun protection factor) in combination with a number indicates how long a sunscreen protects you from UVB radiation and therefore from sunburn. The number for the sun protection factor (SPF) tells you how much longer you can stay in the sun with sunscreen without getting sunburnt – compared to the time your skin can be exposed without protection. This time’s referred to as «self-protection time». It describes how long your skin can stay in the sun naturally, i.e. without sunscreen, before it turns red. The self-protection time is different for everyone and depends on various factors.

It’s therefore crucial to apply cream «thoroughly and generously» to ensure that the sun protection factor marked on the bottle fulfils its purpose on your skin. But what does that mean in terms of quantity? When I watch family and friends applying cream, there’s a wide range of approaches.

«It’s recommended to use 2 mg of sun cream per cm² of skin – for a large person (with around 18,000 cm² of skin) this corresponds to around 2.4 tablespoons of sun cream for the whole body. However, people often apply less than 1 mg per cm².» In order to achieve the required amount, the Swiss Cancer League recommends that you apply a generous amount of cream twice. This way you’re on the safe side regardless of the product and your size.

Jufer also points out that the Swiss Cancer League generally recommends products with a UVA logo and a sun protection factor of at least 30. «For longer periods outdoors or for children, you should use a sun protection factor of 50. What’s also important is that you reapply cream every two hours and after swimming or heavy sweating to maintain protection.» The expert emphasises you should always consider sunscreen as an extra precaution even if you’re in the shade or wearing protective clothing. And shade and clothing should be your first priority, as they offer good protection against UV rays.

Joëlle Jufer is a qualified nurse and health advocate. As a prevention expert at the Swiss Cancer League, her focus is on sun protection. She’s committed to raising awareness of skin cancer prevention and motivating people to take a healthy approach to UV rays. For her, prevention work is an important tool for reducing non-communicable diseases and improving people’s quality of life in the long term.

This article’s the first in a miniseries on sun protection in collaboration with the Swiss Cancer League.

Header image: Natalie Hemengül

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Natalie Hemengül

Senior Editor

Natalie.Hemenguel@digitecgalaxus.ch

As a massive Disney fan, I see the world through rose-tinted glasses. I worship series from the 90s and consider mermaids a religion. When I’m not dancing in glitter rain, I’m either hanging out at pyjama parties or sitting at my make-up table. P.S. I love you, bacon, garlic and onions.

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