Health Centres - Safe in the sun: what's in a sunscreen
We all enjoy the sun, but how we react to its rays varies from one individual to another.
The number of cases of skin cancer has doubled in the last 20 years, which is most probably due to the growing hole in the ozone layer of the sky.
We need to constantly watch out for our skin in the sun. Some people - often those of us who have fair skin - need to take greater care than those who have slightly darker skin.
Why does skin tan?
We all have one thing in common: we tan from staying in the sun because our skin forms the substance melanin.
It is this substance that makes skin darker, and it is the skin's own sun protection.
We form melanin at differing rates, which is why some people tan faster than others and some don't tan at all. People who produce the least melanin, ie those who burn easily, are at highest risk of skin cancer.
The effect of the sun's rays depends on where we are, how strong the radiation is, and what type of skin we have. The sun is strongest the nearer we are to the equator.
How do sunscreens work?
Sunscreens work in different ways to protect us against the rays of the sun. They can have a chemical or physical sun filter or have a mixture of the two.
What's the difference between UVA and UVB rays?
Sun protection factor (SPF) measures the strength of a cream's sun filter against UVB rays.
Sunscreens with a high SPF factor allow you to stay in the sun for longer, but this means you are exposed to more UVA rays.
UVA rays don't burn, but penetrate deep into the skin. They are responsible for cell damage that contributes to ageing and skin cancer.
- Five stars gives 90 per cent of the UVB protection.
What factor should I choose?
Most of us can manage with an SPF 15, and it doesn't make much of a difference if you go for higher factor numbers.
Exceptions are adults who tend to get eczema and children. In these cases, an SPF 25 or higher is recommended.
The sunscreen should also have at least four UVA stars.
Even the highest SPF broad spectrum sunscreen cannot fully protect against UVA and UVB rays. This is why people should cover up and stay in the shade at the hottest times of the day (11am-3pm).
A good tip here is to avoid going into direct sunlight when your shadow is shorter than you are.
Waterproof or water-repellent?
- A waterproof sunscreen withstands 4 x 20 minutes of swimming without being washed off.
These figures only apply if you let yourself air-dry and don't use a towel. It is therefore always a good idea to rub on a layer of cream after going for a dip.
Are there any tips for application?
- An adult should apply a handful of sun cream, equivalent to 30 to 40g. This equals about two tablespoons.
Sun lotion takes time to work, so you need to apply cream half an hour before going out into the sun.
Children should also be covered with light clothing, while babies under 12 months should not stay in the sun at all.
UVB rays burn the topmost layer of skin, causing sunburn and cell damage than can lead to cancerous changes.
- Four stars is 80 per cent.
- Three stars gives 60 per cent.
-
Two stars is 40 per cent.
- One star is 20 per cent.
The SPF you need depends on your skin type.
If you like to go for a swim to cool down, you need to make sure that your sun lotion is either water-repellent or waterproof.
- A water-repellent sunscreen withstands 2 x 20 minutes without being washed off.
Apply cream thickly and often: many people use only a third of the amount of cream they need to achieve the SPF on the bottle. This means they are far less protected than they think.
- A child needs about 20g to cover the whole body.
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