The lowdown on sunscreen

The summer is here (we think!), and naturally you are keen to spend the day outdoors. The first thing that many of us do (if we care about our skin health) is to reach for a hat and the sunscreen. However, if you are confused by sunscreen, you’re not alone.

What is a sunscreen?

Simply put, sunscreen is a substance applied to the skin to reduce the intensity of the sun’s ultraviolet (UV) rays entering the skin and damaging vulnerable skin cells. Sunscreens can take many forms including creams, milks, lotions, gels, foams, oils, ointments and sprays.

The active ingredients of a sunscreen are generally a mixture of organic and inorganic chemicals that absorb UV and convert it into harmless warmth, scatter the incoming UV rays away from the skin and so prevent them entering the skin and causing harm.

The Sun Protection Factor

We normally see something called the Sun Protection Factor, or SPF, on the front of the bottle but what exactly is it telling us?

The SPF is usually taken as how much longer skin covered with sunscreen takes to burn compared with unprotected skin. So, if you burn after 10 minutes in the sun, then using a sunscreen labelled with, say, SPF 15, is taken to mean that you can safely remain in the sun for 10 x 15 = 150 minutes, or 2½ hours, before burning.

What SPF should I choose when I buy a sunscreen?

If preventing sunburn from all day exposure is your goal, we can calculate that for most people with white skin an SPF 15 should, in theory, protect them from sunbathing all day on a beach in southern Europe or Florida as long as the sunscreen is regularly reapplied. But many people who use SPF 15 report getting sunburnt – this is due to a mismatch between manufacturers’ testing and the reality of how much and how carefully you actually apply!

So, to compensate for the difference, an SPF 30 is recommended, especially if you plan to spend several hours in strong sunshine.

Sunscreen Star Rating – what does it tell us?

When you pick up a bottle of sunscreen the first thing you see is the SPF rating on the front of the bottle. But turn the bottle over and on the back is the Star Rating, which can range from 1 to 5 stars, as shown here:

We know that by reducing the intensity, or strength, of the sun’s UV rays on our skin, we reduce the likelihood of damaging our skin – either by getting sunburnt that day or developing skin cancer later in life.

Nature understands the importance of this so that when we seek natural shade by stepping under a tree, or wear clothing to protect our skin, we reduce the overall strength of the sun’s UVB and UVA rays almost equally. In other words, Nature is providing us with balanced protection against both UVB and UVA.

And that’s just what we would like to achieve when we apply a sunscreen to our skin. So how do we know if we are getting balanced protection? That is where the Star Rating comes in. The higher the number of stars, the more balanced the protection.

So, the next time you’re wondering what sunscreen to buy, the first thing to do is to look at the back of the bottle and choose one offering 4- or 5-star protection. Then decide on what SPF you would like. If you are keen to protect your skin as much as possible, you need to choose a sunscreen with SPF 30 or higher.

From a practical viewpoint most sunscreens are now either 4 or 5 stars, so the great majority of modern products are already providing balanced protection.

Tips for applying sunscreen

  • Apply sunscreen liberally to exposed areas 15 to 30 minutes before going out into the sun.
  • Do not rub the sunscreen into your skin but spread the sunscreen as uniformly as possible over the surface of the skin and allow to dry.
  • Re-apply sunscreen to skin 15 to 30 minutes after sun exposure begins.
  • Re-apply sunscreen after vigorous activity that could remove sunscreen, such as swimming, towelling or excessive sweating and rubbing.

Is it safe to use sunscreen on babies?

Ideally this is best avoided in infants less than 6 months of age as babies’ skin is thinner than that of adults, and it can absorb the UV active chemical ingredients in sunscreen more easily, therefore increasing the risk of an allergic reaction. The best approach is to keep infants under 6 months out of direct sun and in the shade as much as possible. This is especially important between the hours of 11 am and 3pm when UV rays are most intense. As well as shade, make sure your child wears loose-fitting clothing that covers the skin and keeps them cool – and do not forget a sunhat. If there is no way to keep your baby out of the sun, you can apply a small amount of high SPF sunscreen to small areas such as the cheeks and back of the hands. Do not forget that babies can easily overheat, which can be extremely dangerous, so shade is best.

Is there evidence that sunscreens prevent skin cancer?

Although there are some data to indicate that sunscreens have a role in preventing skin cancer, we lack the strength of evidence that would be expected before a new drug was introduced as a treatment. This does not mean that we should not be using sunscreen. Just because we don’t have sufficient evidence doesn’t necessarily mean that they are not effective as a way of reducing our risk of skin cancer – and theoretically we would expect them to be, as sunscreens absorb UV and UV is a major risk factor for skin cancer.

Top tip

Make sunscreen application a bit of fun and encourage children to put a dot of sunscreen on each cheek, nose and their chin and carefully rub it in (avoiding the eye area). They can add squiggles of sunscreen to any part of their arms and legs not covered with clothing.

Getting children outdoors and into sport!

Although organised outdoor activity has been curtailed for most of this year, things are slowly getting back to a new normal. The Melanoma Fund, which runs the Outdoor Kids Sun Safety Code is urging parents to check that organisers of activities are ‘OK Accredited’ and if not, ask them to do so. This will ensure that they are keeping everyone sun protected and aware of the risks associated with sunburn. For further details, visit www.oksunsafetycode.com

Brian Diffey

Professor Diffey is an international authority on sun protection and amongst other things, invented the UVA Star Rating adopted by Boots and which remains the world’s longest running measure of UVA protection for sunscreens.

As well as being an Emeritus Professor of Photobiology in Dermatological Sciences at Newcastle University, prior to retiring from the NHS, he was Clinical Director and Professor of Medical Physics at Newcastle General Hospital. Professor Diffey is the Scientific Adviser at the Melanoma Fund.

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