Eight things to know about sunscreen when applying it during the heatwave
If you tend to apply any old factor without paying much attention to the protection you need, or if you swear you’re a factor 15 person but end up burning, a simple sunscreen calculation can be necessary.
It’s tempting to assume that your personal SPF is a simple calculation of the time you take to burn multiplied by the factor. So if you burn after 10 minutes in the sun, using a sunscreen labeled with SPF15 should mean you can safely stay in the sun for 150 minutes before you burn. But for most people, that won’t be the case.
The British Association of Dermatologists says a safer way to think about it is that applying SPF15 sunscreen results in UV exposure “one-fifteenth of that you would have received had you not applied no sunscreen”.
Animal, vegetable or mineral, how “natural” should your sunscreen be?
Sunscreens are often divided into two camps, referred to on the packaging as “mineral” or “chemical.” The names are slightly misleading, says Professor Diffey, because all sunscreens contain chemicals. More specifically, sunscreens contain either organic or inorganic UV filters or, like most basic sunscreens on the market, a mixture of the two.
“What manufacturers tend to do these days is use two or three organic chemicals and they mix that with an inorganic chemical like titanium dioxide,” Prof Diffey says.
Inorganic filters like titanium dioxide and zinc oxide are often called “physical” or “mineral” because they “reflect and scatter UV rays,” says Dr. Fassihi. They are commonly found in children’s sunscreens and can leave a white residue on the skin and feel a bit greasy.
“The chemical ingredients in sunscreens are effective at absorbing UV rays and are cosmetically much more acceptable,” says Dr. Fassihi. They tend to have a lighter feel, which means they go on easier.
For Dr Sarah Tonks, dermatologist at the Lovely Clinic in London, chemical sunscreens are prohibited. “I don’t use any chemical sunscreen. Firstly it gives me acne and secondly I worry about the [impact on the] coral.”
National Geographic estimates that 14,000 tons of sunscreen pours into our oceans each year, which can be toxic to marine life and coral reefs. Earlier this year, Holland & Barrett banned chemical sunscreens. Meanwhile, dermatologists say “mineral” sunscreens tend to irritate your skin less.
Ultimately, they both protect the skin, so the best thing to do is find one that you find really pleasant to apply.
Once-a-day sunscreens don’t work
Who? tested once-a-day sunscreen in 2016, seeing a 74% decrease in protection at the end of the day. Cancer Research UK and the British Association of Dermatologists advise against their use, and it should be noted that they are banned in Australia. They may give you a false sense of security when you may well rub the cream on your clothes and find that the protection diminishes after a swim.