But while many of us think that opting for SPF 30 and above is enough protection in itself, a new study published in Acta Dermato-Venereologica has found that we might not be applying enough of it for it to be effective in safeguarding our skin from the harmful effects of UV, such as burns and skin cancer.
Conducted by researchers at King's College London, the main aim of the study, in which 16 young people took part, was to look at how SPF sunscreen works to prevent sun damage in sensitive skin types. In a number of tests, volunteers applied varying quantities of "a very high SPF formulation" – exactly 0.75, 1.3 and 2.0mg of sunscreen per square centimetre of skin – before being exposed to ultraviolet light. DNA damage was then assessed in each volunteer.
By carrying out these tests, the researchers discovered that "sunscreen may not fully inhibit sunburn because people typically overestimate protection indicated by the label by using much less sunscreen than [the required] 2 mg/cm2". That's 2mg of sunscreen (roughly one quarter of a teaspoon) per every square centimetre of skin. Put simply, the study suggested that a lot of us aren't applying sunscreen thickly enough to see the full benefits, despite the fact it might be a high factor, such as 30 or 50. According to professor and study leader Antony Young, most people apply sunscreen at 0.75mg, which then lowers the level of protection. "People are typically getting much less protection than they think," he told the Guardian. "For example, if you get SPF20 and use at a lower thickness of 0.75 milligrams per centimetre squared, your level of protection could be as low as SPF4."
The data also suggests that using sunscreen is likely to reduce the risk of skin cancer but that people need to be better informed on how to best use sunscreens in public health campaigns. According to dermatologist and author of The Skincare Bible, Dr Anjali Mahto, healthy sun-seeking behaviours should be encouraged, too. "This includes wearing broad spectrum SPF of 30 and above, seeking shade during peak daylight hours, protective clothing and use of hats and sunglasses," she told R29. "It is also important to note that there is no sunscreen that gives 100% protection against the sun," Dr Mahto continued.
"The SPF gives no indication whether a sunscreen is also offering you protection against UVA. UVA rays penetrate the skin deeper than UVB and are traditionally associated with ageing of the skin. Sunscreens sold in the EU have a 'star rating' for UVA or 'UVA logo' on the label. Most modern-day sunscreens are broad spectrum which means they will provide protection against both UVA and UVB. Choosing the correct sunscreen for your skin largely comes down to personal preference, but my personal favourites are Heliocare 360 Gel Oil-Free SPF 50, Avène Cleanance Solaire SPF 30 and SkinCeuticals Mineral Matte UV Defence SPF 30."
The news comes after a similar study presented at the British Association of Dermatologists' annual meeting in Edinburgh, in which experts found that the SPF in our trusty pot of moisturiser, whatever the factor, might not be offering us the UV protection we think it is.