If you forget to bring the sunscreen on your way to the beach, timely research is giving you a good reason to buy a bottle while en route. A new study suggests that applying SPF 30 drastically cuts your risk of developing melanoma, the nastiest form of skin cancer.
American researchers out of Ohio State University say that applying sun protection 30 – or SPF 30 – doesn’t just protect against burns, it cuts melanoma risk by 80 per cent. At least in mouse models it did.
“Sunscreens are known to prevent skin from burning when exposed to UV sunlight, which is a major risk factor for melanoma. However, it has not been possible to test whether sunscreens prevent melanoma, because these are generally manufactured as cosmetics and tested in human volunteers or synthetic skin models,” lead researcher Dr. Christin Burd said in an university statement.
“We have developed a mouse model that allows us to test the ability of a sunscreen to not only prevent burns but also to prevent melanoma. This is a remarkable accomplishment. We hope that this model will lead to breakthroughs in melanoma prevention,” Burd said.
READ MORE: What you need to know about sunscreen and protecting your skin
To test the efficacy of sunblock when it comes to staving off skin cancer risk, Burd and her team worked with mice and a handful of different SPF 30 sunscreens.
Their findings build on previous research in which they built a mouse melanoma model that had genetically engineered mice develop melanoma at about 26 weeks. They were given a chemical called 4-hydroxytamoxifen (4OHT) that made them predisposed to developing the skin cancer.
This time around, the researchers figured out how quickly the rodents ended up with skin cancer after they were exposed to a single dose of UVB light daily.
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Then they gave the mice SPF 30 to stave off the disease. Turns out all of the products which were marketed as UV-blocking options delayed the onset of melanoma and even reduced the odds of tumours.
“Melanoma-free survival was reduced by 80 per cent,” Burd said. There were “minor differences” in how protective the sunblocks were against melanoma, but that’s because some had a higher rating than the SPF 30 they were labelled as.
Burd conceded that there were some limitations to her findings, too.
For starters, the study focused on rats and not humans, and researchers only worked with short, intense bursts of UVB rays – it was equivalent to a week’s long beach vacation.
“Sunscreens were never meant to handle a week’s worth of sun given at one time, and we are working to reduce the UVB dose we use in our studies,” Burd said.
There are three types of UV rays, too. This study only factored in UVB.
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The three spectrums of light include: ultraviolet A (long rays), which is tied to aging the skin; ultraviolet B (short rays), which can lead to burns; and ultraviolet C, which isn’t as worrisome because most of the rays are absorbed by the ozone layer.
UVA and UVB can contribute to skin cancer and damaging your skin.
“Both are carcinogenic in different ways so it’s important for sunscreen to block both,” according to Dr. Anatoli Freiman. He’s a dermatologist and medical director of the Toronto Dermatology Centre.
What should you look for in a sunscreen?
The Canadian Dermatology Association recommends a sunblock with an SPF 30 or higher. It should also come with broad spectrum protection – this protects you from UVA and UVB rays.
An SPF 30 would cover off about 97 per cent of UVB rays, but wearing a higher SPF may be your best bet because it’ll be more effective. It’s easy for consumers to miss spots or apply too little to certain parts of their body so the higher protection would compensate, Freiman said.
If you’ve had skin cancer or a strong family history of the disease, stick to a higher SPF.
How often should you apply sunscreen?
Sunblock should be applied 15 minutes before going outside. If you happen to forget and head out, apply it as soon as possible anyway – Freiman says it should start working immediately.
“It should be reapplied every two hours when you’re exposed to sunrays. If you’re sweating, swimming or exposed to water, you may need to top up more often,” Freiman advises.
How much sunscreen should you be using?
As a general rule of thumb, if you’re applying sunscreen from head to toe, use a shot glass-sized amount – or two tablespoons. Use half of a teaspoon for each part of your body – half of a teaspoon for your face, another half for your left leg, for example.
Sunscreens can be applied as lotions and even aerosol sprays. The sprays are seen as more finicky because you can’t tell if you’re applying it evenly but the experts say your decision-making in this case is up to personal preference.
If you want a chemical-free sunblock, Freiman says options with zinc oxide are readily available, too.
If you spend a lot of time in the water, opt for a water-resistant sunblock.
carmen.chai@globalnews.ca
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