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CTPA challenges the Which? report and explains why we can be confident in water resistant sunscreens

24 May 2018

This week Which? Magazine has published its annual report about sunscreens.  Disappointingly Which? has chosen to raise a number of questions about water-resistant sunscreen safety which could alarm consumers – and even discourage them from using sunscreens as part of a sunsafe regime. Which? also offers outdated sun safety advice that could prove harmful to consumers. The Cosmetic, Toiletry and Perfumery Association (CTPA) is concerned by this.

Water resistant sunscreen myths debunked and the science explained

These products are water-resistant, not waterproof, however they offer a much higher level of protection than the Which? test on two anonymous products suggests.

To help explain why consumers can trust their sunscreens, and to ensure they don’t miss out on the important protection that sun protection products provide, CTPA is sharing the facts about the science behind sunscreen safety and efficacy.  Dr Chris Flower, Director-General of CTPA, describes the science behind water resistant sunscreens:

Dr Chris Flower, Chartered Biologist and toxicologist and Director-General of CTPA, said:

The aim of the validated test method used by suncare manufacturers is to determine that the sunscreen will not be completely washed off while being worn in the water.  Interestingly, tap water is used in the test as it is a more harsh solvent than salt or chlorinated water.  To pass the test, a product must retain at least 50% of the initial SPF value after immersion in water. In fact an SPF 30 product will stop approximately 96% of UV rays reaching the skin and after robust water resistance testing the product will still filter out at least 93% of the sun’s UV rays.  Clearly not the dramatic reduction in efficacy that Which? implies.  However a non-water-resistant product could be washed off the skin completely meaning no protection from UV rays (until reapplication).

Of course we should always follow the instructions and re-apply our sunscreens regularly and especially after we have been swimming or towelling dry, even water-resistant products.   The ‘dry’ SPF number is a far more realistic indicator of the product’s protection for all round use, while still offering protection after time in the water.

Manufacturers develop water-resistant sunscreens to be less easily removed when worn in water. These products may be labelled as water resistant or very water resistant.  We are absolutely clear: that no product is 100% waterproof; just as no sunscreen can provide 100% protection.   The term “sunblock” should not be used on sun protection products and importantly sunscreens should never be used to spend longer in the sun.

Dr Rachel Abbott, Consultant Dermatologist and British Skin Foundation spokesperson said:

"Rather than relying on sunscreen for protection in the water, consider avoiding swimming between 11am-3pm when the UV index is at its highest, wearing a 'rash vest' and shorts or using a 'sunsuit' for kids together with a broad brimmed hat or legionnaire style hat for kids when possible. Although some sunscreens claim to be water resistant, it's important to remember that this doesn't mean they are waterproof. Swimming and towel drying can remove the sunscreen, in addition to it rubbing off over time."

Be sunsafe!

CTPA is also extremely concerned to see that Which? is telling its readers that if they burn in 10 minutes in the sun, using an SPF 30 sunscreen would allow them to stay in the sun for 300 minutes. This is contrary to all the advice given by experts on sun protection, and CTPA recently wrote to Which? to emphasise this.

Sunscreens should never be used to spend longer in the sun; they are an essential part of a sunsafe regime that involves avoiding strong sunshine by seeking shade and covering up with clothes and a hat, as well as protecting the skin with an appropriate sunscreen when exposure to the sun is unavoidable. To promote staying longer in the sun is extremely irresponsible and potentially dangerous.

Dr Emma Meredith, Director of Science at CTPA and a pharmacist, said:

“Which? rightly notes the concern about malignant melanoma.  All public health authorities globally recommend the use of sun protection products as part of a sunsafe regime to help reduce the risk of skin cancer.  Recent results* from Cancer Research UK have highlighted that UV radiation is the third biggest contributor to cancer cases in the UK.  It is therefore irresponsible of Which? to not only encourage spending longer in the sun but also to undermine confidence in sunscreens that are strictly regulated and robustly assessed by manufacturers.”

Sunscreen science in-depth

Understanding the testing process: the robust science behind water-resistant sunscreen safety and efficacy

  • The laws covering the manufacture of cosmetic products require that products have to do what they say they will do.  Not only are sunscreens thoroughly assessed for safety but any claim made, including SPF, UVA protection, water resistance and ‘extended wear’, has to be substantiated and this takes robust data.  All of this information must be kept by the company and is open to review by the authorities, who monitor compliance with the law via in-market controls.  In the UK, this is Trading Standards. 
  • The recognised industry test method for water resistance assesses and compares the SPF before water immersion and after a fixed period of water immersion to determine that the sunscreen will not be completely washed off while being worn in the water.  The ‘dry’ SPF number is a far more realistic indicator of the product’s protection for all round use, while still offering protection after time in the water.
  • The test method that companies across the UK and EU use to determine water resistance for sunscreens has undergone scrutiny by experts to make sure it is repeatable (which means you get the correct results over and over again when carried out in the same laboratory) and that it is reproducible (which means the results are reliable wherever in the world they are conducted). 
  • Water resistance testing for sunscreens is currently going through a global review by international suncare experts to make sure wherever it is used in the world we can be confident it is standardised.
  • It is important to note that the official testing process uses tap water as it is a more harsh solvent than salt or chlorinated water and is scientifically more relevant when testing water resistant sunscreens.


Understanding the process: the science behind Europe’s gold standard sunscreen laws

  • When creating a sunscreen, companies decide what level of SPF they want in the product.
  • Scientists with expert suncare knowledge will use their wealth of experience and expertise to select the UV filters they want to use and judge how much is needed to formulate a product with the intended SPF and UVA protection. 
  • During development, the product is tested by scientists a number of times using specialist equipment, and sometimes human volunteers, to check the SPF is consistently on track. 
  • If at any stage during the process the SPF isn’t correct, then the product will not be taken any further. 
  • If the development tests all confirm the required SPF, then the product will go on to have final SPF testing on human volunteers. 
  • This lengthy and complex process carried out by manufacturers provide the assurances that the sunscreen does what it is supposed to do and has been made correctly.
  • Which? is not able to follow all of this testing process.  It bases the results of the sunscreen report on just one or two final SPF tests which is why its results must be seen as highly questionable. 


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