When Dr Roopal Kundu, a US dermatologist, carried out a study to determine people’s knowledge of sun protection, she expected a certain level of misunderstanding.
What surprised her was that even those people who had family members with skin cancer did not know how to protect themselves properly from the sun.
In her 2015 study, published in the journal JAMA Dermatology, just 43 per cent understood the definition of the SPF value or sun protection factor.
Only 55 per cent correctly identified the amount of sunscreen needed to cover their body to achieve the correct level of sun protection.
And just over a third of participants knew that being designated “broad-spectrum” was important for choice of sun lotion.
There are two types of radiation both of which cause cancer. UVA radiation is associated with accelerated skin ageing and UVB exposure is associated with sunburn. The SPF rating only indicates protection from UVB rays. When a sunscreen protects against both, it is known as broad-spectrum protection.
In the UK, there appears to be more misunderstanding. A study of 2,000 people by the Royal Pharmaceutical Society, also in 2015, found only 8 per cent of people surveyed knew the SPF rating on the product label referred to protection from UVB rays only. One in four did not know what the SPF rating stood for at all.
Sun cream is big business in the UK – we spend £200 million on products every year – and there is a myriad to choose from. One study found there were 6,500 products categorised as sunscreen on Amazon.com.
But choosing one is complicated. As well as the SPF, which ranges from 2 to 50+, there is a voluntary 0 to 5-star rating in the European Union, indicating how much UVA light is absorbed in comparison to UVB. This means that even if a product has a high star rating, it may not give enough UVA protection if the SPF is low.
Professor Jayne Lawrence, Royal Pharmaceutical Society chief scientist, says: “At the moment, bottles of sunscreen typically have the SPF number on the front, the UVA stars somewhere on the back, brand information and lots of small-print instructions. It’s hard to make sense of it all and I’m not surprised there’s confusion.”
So what should consumers be looking for?
SPFs are categorised as low (6 to 14), medium (15 to 29), high (30 to 50) and very high (50+). The UVA protection should be at least a third of the labelled SPF. A product that achieves this will be labelled with a UVA logo (UVA printed in a circle).
The British Association of Dermatology (BAD) recommends using SPF 30, with a UVA rating of 4 or 5 stars. This should be combined with using shade and protective clothing.
Look for sunscreen marked photostable, which means the filters do not break down in the sun.
Some moisturisers have an SPF rating, commonly of 15. But BAD says these formulas are less likely to be rub-resistant and water resistant, and are likely to be applied a lot more thinly so are unlikely to offer the same level of protection.
SPF moisturisers may not contain any UVA protection and as a result will not protect against UV ageing.
BAD says the minimum to apply is at least six full teaspoons (approximately 36 grams) to cover an average adult, which is more than half a teaspoon of sunscreen to each arm, to the face and neck including the ears, and just over one teaspoon to each leg, front of the body and back.
Reapply at least every two hours, and immediately after swimming, perspiring and towel-drying or if it has rubbed off.
Sunscreens generally have a shelf life of two to three years if they are stored at the correct temperature and not left or kept in direct sunlight. Do not exceed the expiry date.