How to walk under the sun and not burn out

In summer, everyone is looking for a way to get to the beach at least for a while. But, as the personal experience of our editors shows, even one single day under the sun can turn into sunburns that will “please” you for the next week. Obviously, quite a lot of people are facing this problem. Journalists Science Focus We decided to find out how sunscreen works and how to use it correctly. With questions, they turned to Brian Diffie, a member of the British Association of Dermatologists and Emeritus Professor of Photobiology at Newcastle University.

Should I use sunscreen in the shade?

Yes need. Ultraviolet is scattered in the atmosphere. When you’re in direct sunlight, half of your UV radiation comes directly from the star. The other half hits your skin just from the atmosphere. So even hiding under a canopy or a beach umbrella, you can still get burned, albeit twice as slowly.

Why is it so easy to get burned on the beach?

Many people think that it is easy to get sunburned on the beach because the UV reflects off the surface of the water. It is not true. So little ultraviolet is reflected from the surface of the water that it should not be taken into account.

The main reason is that the beach is open on all sides. If you are not hiding in the shade, then you get a full dose of ultraviolet — both the one that comes from the sun and the one that is scattered in the air. That is, in the desert or in an open field, you would burn out as quickly as on the beach, although there is no water there.

How to apply sunscreen?

On tubes, they usually write that it should be rubbed into the skin, but do not write how much it needs to be done. Because of this, many people try to rub the cream almost dry. You don’t need to do this.

The job of sunscreen is to form a barrier between UV rays and the living cells of your skin. If you rub the cream too hard, it goes deep into the skin, and the top layer of epidermal cells remains unprotected. The cream does not need to be rubbed hard. It is enough to smear it on the skin and let it dry.

How much cream should be applied?

When cream developers test the sun protection factor (SPF), they focus on a volume of 2 milligrams per centimeter of skin. This is a kind of international standard that all manufacturers follow. Unfortunately, consumers do not follow this standard.

According to Prof. Diffie, people typically apply half as much cream as recommended by the manufacturer (about 1 milligram per centimeter of skin). This is due to the fact that a layer of two milligrams seems too thick to them. If you’re using sunscreen, you’re probably smearing too much too. As a result, where the manufacturer claims SPF 30, in fact, there are from 10 to 15. But this is not a problem. Professor Diffie recommends applying the cream twice. The second time — after about half an hour, when the first layer dries.

Do I need to use sunscreen daily?

It doesn’t make any sense. In winter, sunscreen is definitely not needed. In summer, it is worth using it only on the beach. If you spend half an hour a day on the street, on the way from home to work and back, then nothing bad will happen to you without a cream.

Are expensive creams better than cheap ones?

No. Buying a more expensive cream, you pay not for additional protection, but for aesthetics. A more expensive cream may smell better or spread better on the skin. But the protective substances in expensive and cheap creams are the same.

Is a high SPF better than a low one?

I guess, yes. But it should be borne in mind that the higher the SPF, the more difficult it will be to smear the cream. Creams with a high SPF can be very viscous. Therefore, sometimes it is more convenient to simply apply a cream with a low SPF several times.