You don't need to use suncream above SPF 30 - but there's another rating you should be looking at

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• Sunscreen with a high SPF rating is the best protection for your skin from harmful UV rays.
• But there's another rating you should be looking at too.
• It's called the star rating, and you should buy a suncream with a rating of at least 4.

It's really hot. That means the roof terraces, beer gardens, and parks are all rammed full of people soaking up the rays.

But it also means bad tan lines and sunburn - especially among those people who "refuse to wear sunscreen in the UK."

Sunscreen is the best protection you have against the harmful UVA and UVB rays from the sun. UVA radiation affects elastin in the skin, so prolonged exposure causes wrinkles and brown pigmentation, as well as skin cancer. It penetrates the skin more deeply than UVB rays, which cause sunburn and also types of skin cancer.

A sunscreen with high SPF (which stands for sun protection factor) will block the rays by absorbing them and giving the energy back out as infrared.

A common belief is that the higher the SPF, the better the protection. While this is true, you don't actually have to wear anything above SPF 30, as Twitter user Jonathan Hume pointed out.

According to the British Association of Dermatologists, SPFs are rated on a scale of 2-50+ based on the level of protection they offer. But SPF 30 blocks 97% of UVB rays, and SPF 50 blocks 98%, so the increase in protection above 30 is pretty minimal.

"We recommend a sunscreen with an SPF of 30 as a satisfactory form of sun protection in addition to protective shade and clothing," the BAD says on its website.

There's also another rating you should look at for protecting your skin. It's called the star rating, and it's a measure of how much UVA is blocked.

The scale goes from 0 to 5, with 3-star cream blocking about 60% of the amount of UVA as UVB rays. Basically, you want a suncream that is at least 4-star.

"Be aware that if you choose a low SPF it may still have a high level of stars, not because it is providing lots of UVA protection, but because the ratio between the UVA and UVB protection is about the same," the BAD says. "That's why it's important to choose a high SPF as well as a high UVA protection."