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Everything you need to know about sunscreen

The You & Yours podcast, Smart Consumer, has been tackling the slippery subject of sunscreen - from SPF dilemmas to reef-friendly labels.

Here are a few fascinating facts, hints and tips about summer’s hottest accessory.

Clinical Dermatologist Dr Andrew Birnie’s top five suncream tips

1. Apply 15 to 20 minutes before going out. Actually, it works instantly, but if you allow this time it will go into the skin better and it’s less likely to rub off on clothes or run off with sweat.

2. How much should you put on? Typically the recommendation is about a teaspoon’s worth for each body part. I find this quite a difficult concept in practice, therefore I usually just say you need to put enough on to make your skin look white before rubbing it in.

3. How often should you put it on? It is difficult to give a one size fits all answer, so here is my personal practice: I apply daily after shaving and extend it up to my forehead, temples and down onto my neck. I don’t normally apply to the rest of my exposed skin unless I’m going to be out for more than about 20 minutes. Of course, if you’re fair you might need to apply after less time.

4. Don’t rely on sunscreen alone. Use hats, rash vests or clothes, and sunglasses. Avoid the peak times; 11 am to 3 pm. This is not necessarily the hottest part of the day, it’s because the UV strength is highest at around midday.

5. Don’t rely on make up with SPF for proper protection. Whilst it’s better than nothing, one rarely puts enough on and they really protect against the longer UVA wavelengths.

When was sunscreen first invented?

Most sources would credit Swiss scientist Franz Greiter as the true inventor of sunscreen. As a chemistry student, he suffered sunburn whilst mountain climbing and set out to try and invent a preventative solution. His Gletscher Crème (Glacier Cream), which came to market in 1946, was the first commercially viable sun protection cream.

Across the pond, a Florida physician called Benjamin Green invented a sunblock to protect the GI’s in the South Pacific from sunburn during WWII. It was called “Red Vet Pet” because it was made from red veterinary petrolatum. He later improved his formula, adding cocoa butter and coconut oil, to create Coppertone suntan cream - the first commercially mass-produced sunscreen in the United States, which launched in 1944.

Both Greiter and Green’s products would have been thick and pasty and felt more like paint than the sunscreen we use today.

Mineral suncream vs chemical suncream

Lots of companies have been launching mineral suncream products. Are they better for you?

When was the first water resistant sunscreen?

Water resistant sunscreens were introduced in 1977.

Be aware that water resistant does not mean waterproof! Current UK tests allow manufacturers to label a sunscreen as water resistant if the SPF drops by up to 50% after two 20-minute periods in water, so it’s always safer to top up after you towel off.

What does SPF stand for?

SPF stands for Sun Protection Factor. It tells what percentage of ultraviolet B radiation (UVB) will reach the skin and therefore how long a sunscreen will protect you for. SPF 30 means that 1⁄30 of the burning radiation reaches the skin through the sunscreen. The Swiss Greiter is also the brains behind this rating system, which he introduced in 1962. It has since become the worldwide standard for measuring the effectiveness of sunscreen.

Remember: water resistant does not mean waterproof!

What do the stars on my sunscreen mean?

You may notice a UVA star rating on your bottle. The stars, ranging from 0 to 5, indicate ultraviolet A radiation (UVA) protection.
It’s important to choose a high SPF as well as a sunscreen with a high number of stars. Sunscreens that offer both UVA and UVB protection are sometimes labelled “broad spectrum”. If your SPF is 30, look for a UVA rating of 4 or 5 stars.

It’s important to choose a high SPF as well as a sunscreen with a high number of stars. If your SPF is 30, look for a UVA rating of 4 or 5 stars.

What’s the difference between chemical and physical sunscreen?

In 2018, the state of Hawaii passed a new law banning the sale and use of certain sun creams thought to be harmful to coral reefs. The fear about certain chemicals has led to an increase of mineral sunscreens on the market.

The simple difference between a physical and a chemical sunscreen is that one sits on the surface of your skin and deflects rays and the other absorbs into your skin and absorbs the rays. Physical sunscreens that sit on the skin are typically made of either zinc oxide or titanium dioxide and work by reflection and scattering. The UV rays hit them and bounce off. A chemical sunscreen works by performing a very simple chemical reaction where they turn the UV energy into heat and that heat is then released.

People with sensitive skin or skin conditions will often fair better with a physical sunscreen.

Is there a sunscreen that combines both chemical and physical?

There are more sophisticated sunscreens out there now that are able to both absorb and reflect the sun’s rays. These are known as micronized filters. They are technically made from chemical sunscreen ingredients but they also have some reflection and scattering properties. This makes them more efficient and they need fewer ingredients to be effective.

How long can I keep my sunscreen for?

Sunscreens are designed to remain effective for up to three years. Some sunscreens will have an expiration date, after which you can’t expect them to work to full strength. If there’s no date, don’t risk it. Make a note on the bottle of the year you bought it so you know when to restock.

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