How to choose a sunscreen

UVA, UVB, SPF, what do they mean when it comes to protecting your skin?


We’ve come a long, long way from when my parents used to slap on the ‘sun tan oil’ during those rare days of summer sunshine we'd enjoy at the beach or in the garden.

My Dad would lie motionless for hours, looking like a beached walrus with the sun glinting off his oily hide.

I don’t know to this day whether it was true or not, but I swear he believed the lotion he was using actually caused his skin to brown more quickly. He was literally basting himself.

Nowadays we know better and ‘sun tan oil’ has evolved into ‘sunscreen’.

With that evolution, however, has come a scientific benchmarking system that allows the user to choose from a range of protection levels depending on their perceived need.

Unfortunately the scale used is not exactly clear. It is intuitive enough for most of us to understand that an SPF15 offers less protection than an SPF30 or SPF50, simply because the value is lower.

So far so obvious, but what does it actually mean?

Well it surprises many to discover that the number actually relates to the time it will take the skin to start to redden and burn on any given day.

A sunscreen with an SPF (sun protection factor) of 15, for instance, will allow your skin 15 times longer in the sun before it feels the effects of the sun than if you wore no protection at all.

Depending on your location, the weather and your skin type, that could mean hours; or it could mean 15 minutes.

With this protection comes danger. We are now all aware that prolonged exposure to the sun's rays can cause wrinkles, premature ageing, skin abnormalities and even cancer.

The culprit is UV (ultra violet) light which is, quite simply, a form of radiation and prolonged exposure to it can lead to damage to the skin's DNA.

It is worth remembering that UV light is precisely what sunbeds use to tan the skin.

Outside of the visible light spectrum, the shorter wavelengths of UV light are classified into three broad categories; UVA, UVB and UVC.

UVC, the shortest and most damaging wavelength, is more or less wholly filtered by the ozone in the earth’s atmosphere (one of the reasons why the hole in the ozone layer caused such a stir).

The UVA and UVB rays that do reach us are both likely to cause damage over time although UVB is considered the most dangerous.

The SPF rating relates to the level of protection offered against UVB.

UVA light is what makes the skin tan and so some sunscreens offer the option of lesser protection against UVA.

In Europe and the UK, at least for the time being, UVA protection is measure by using a five-star rating separate to the SPF, one star being the lowest level of protection and five stars being the highest.

Products offering protection against both UVA and UVB are known and labelled as ‘broad spectrum’ sunscreens which experts highly recommend using.

Cancer experts recommend a minimum SPF of 15 and at least a four star UVA rating to provide meaningful protection.

Where children are concerned it is worth erring on the side of caution. Scientists estimate that around a quarter of the total lifetime exposure to sunlight occurs before the age of 18, so make sure they are protected.

They may not thank you now, but in a few more years their skin will be very grateful indeed.


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