Sunscreen May Offer Much Less Protection Than We Thought

Peter Russell

July 25, 2018

Heatwave alerts and warnings to stay out of the midday sun have become a familiar feature of summer 2018 in the UK. Now, a new small study has warned that we may be getting less protection from sunscreen than we think.

Previous research has found that most people apply less than half of the amount of sunscreen required to provide the level of protection indicated on the packaging. The latest study, published in the journal Acta Dermato-Venereology, found that sunscreen with a sun protection factor (SPF) of 50, applied too thinly, may only provide 40% of the protection from the sun than people might suppose.

Fair Skin

The findings were based on research led by King's College London which assessed the level of protection people actually received based on typical sunscreen use.

The investigation involved a cohort of 16 healthy young volunteers with fair skin who were divided into two groups of eight, each consisting of five men and three women.

One group received a single dose of solar simulated radiation to areas treated with high SPF sunscreen applied in thicknesses of 0.75mg, 1.3mg, and 2mg/cm2.

The other group received doses of solar simulated radiation on 5 consecutive days, designed to mimic typical holiday exposure to the sun experienced in destinations such as Tenerife in the Canary Islands, Florida in the US, and São Paulo in Brazil.

DNA Damage

Biopsy tissue samples taken from the skin of those exposed to repeated doses of UVR showed "considerable" DNA damage in areas that had not been protected by sunscreen. Less damage was seen when sunscreen was applied at a thickness of 0.75mg/cm2 and considerably reduced when 2mg/cm2 of sunscreen was applied, which is the amount manufacturers use to test SPF levels of their products.

Five days of exposure to high dose ultraviolet radiation (UVR)  with the sunscreen at 2mg/cm2 showed much less damage than a single day's low UVR dose exposure without sunscreen across all samples, the researchers reported.

Prof Antony Young from King's College London, who led the study, said: "There is no dispute that sunscreen provides important protection against the cancer causing impact of the sun's ultra violet rays. However, what this research shows is that the way sunscreen is applied plays an important role in determining how effective it is.

"Given that most people don't use sunscreens as tested as tested by manufacturers, it's better for people to use a much higher SPF than they think is necessary."

The study concluded that "there should be more emphasis in communicating how to best use sunscreens in public health campaigns".

The study authors acknowledged that a major weakness of their investigation was the small number of volunteers involved.

'We Need to Use a Higher SPF'

Nevertheless, Nina Goad from the British Association of Dermatologists (BAD) commented: "'This research demonstrates why it's so important to choose an SPF of 30 or more. In theory, an SPF of 15 should be sufficient but we know that in real-world situations, we need the additional protection offered by a higher SPF.

"It also shows why we shouldn't rely on sunscreen alone for sun protection but we should also use clothing and shade.

"An extra consideration is that when we apply sunscreen, we are prone to missing patches of skin, as well as applying it too thinly."

Advice from the BAD is:

  • Apply sunscreen to commonly missed area, such as the back and sides of the neck, temples, and ears

  • An average adult should apply at least 6 full teaspoons (approximately 36 grams) of sunscreen

  • Apply sunscreen 15 to 30 minutes before going out in the sun

  • Reapply sunscreen every 2 hours, and immediately after swimming, perspiring and towel drying

'Stay Out of the Sun'

The current heatwave is set to continue over many parts of the UK this week. A 'heatwave action' level 3 alert has been issued in England for the Midlands, Eastern, and South-East England.

Dr Thomas Waite, consultant in health protection at Public Health England, said: "To beat the heat, try to keep out the sun from 11am to 3pm, walk in the shade if you can, apply sunscreen and wear a hat if you have to go out in the heat. Also try to carry water with you when travelling."

Sub-optimal Application of a High SPF Sunscreen Prevents Epidermal DNA Damage in Vivo, Acta Derm Venereol 2018 Epub ahead of print.

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