I always get surprised by what patients say in clinic. Last week, I was advising a patient on sunscreen use and he stopped me short. He is a long-distance cyclist and he told me that he buys kilos of sunscreen at the start of the season.
I started congratulating him for his foresight and the implication that he uses plenty and liberal amounts of sunscreen. Before I could continue on to which brands I would recommend, he wanted to point out that he had already bought his annual couple of kilos of sunscreen.
This then required the obvious question of which sunscreen he had bought. The information was proffered with a hopeful face and I’m afraid my expression must have looked rather grim because his faded to match mine rather rapidly.
Why? What was the problem?
The problem was that he had purchased a huge amount of a sunscreen marketed as a ‘once a day’ sunscreen.
But they’re really good, aren’t they?
Dermatologists are always preaching about using a high factor (high SpF), broad spectrum (high star rating) sunscreen, applied liberally and frequently for optimum sunscreen use. We recommend sunscreens are applied every 2 hours. Studies have shown that we all apply far less sunscreen than that recommended to achieve the SpF on the bottle.
[Stenberg C, Larkö. Sunscreen application and its importance for the sun protection factor. Arch Dermatol 1985;121(11):1400-2.]
We actually apply only a quarter to a third the recommended amount of sunscreen. This, in reality, equates to only a quarter to a third the SpF on the bottle. So if you apply a sunscreen of SpF 10, you really are only getting an SpF 2.5 to 3 and if you apply a sunscreen of SpF 20, you really are getting only an SpF 5 to 6!
Avoidance of the sun is, of course, the best sun protection and this is achieved by either staying out of the sun or wearing protective, dense-weave clothing in the sun.
What is the star rating?
The SpF relates to the level of protection against UVB rays and the star rating relates to the level of protection against UVA rays hence why high SpF and 5-star rated sunscreens are what we recommend. UVA rays are able to penetrate farther into the skin and can be more damaging and hence protection from UVA is just as important as protection against UVB rays.
Aren’t these ‘once a day’ sunscreens like that?
Well, they may be of a high SpF and high star rating, but not all are. However, they are marketed purely on the basis that they provide sun protection for an extended period of time, usually 8 hours or all day, the implication being that you just have to apply once a day and will get the same level of protection for that suggested period of time.
So I’m guessing that they don’t do that?
‘Which?’ has just conducted a test on these once-a-day sunscreens to see if they really deliver what they promise.
How did they test them?
They tested four common brands of ‘once a day’ sunscreens. They applied them to a small patch of skin on the back of volunteers and shone a UV lamp on that area. The smallest dose of UVB light required to turn the skin red, with or without the sun cream was recorded.
This test was then repeated six to eight hours later.
What did they find?
They found an average 74% reduction in SpF protection after six to eight hours.
They did, however, allow the volunteers to wear a t-shirt and sit on a chair in the lab for the six to eight hour waiting period.
But most of the sunscreen would have been rubbed off, surely!
That is true, it probably is. And if you think of what you do on holiday, we most probably would put a t-shirt or blouse on at points during the day and sit on a chair or sunlounger over a six to eight hour period. We also would probably get sweaty or go swimming which would go further to rubbing more of the sunscreen off.
So what do ‘Which?’ recommend?
They state that ‘once a day’ sunscreens are not allowed in Australia where the manufacturing and labeling of sunscreens is strict and the ‘once a day’ claim is thought to be misleading. A spokesperson for the Australian Theraeutic Goods Association stated that there is no test data to support the ‘once a day’ claim.
The recommendations in the UK (by the British Association of Dermatologists and Cancer Research UK) are to not rely on these ‘once a day’ sunscreens to provide adequate sun protection for extended periods of time in the sun but to use them as you would any other sunscreen.
[http://www.which.co.uk/reviews/sun-creams/article/once-a-day-sun-creams]
Yours sincerely,
Sandy
Dr Sandy Flann, Consultant Dermatologist.
