What you need to know about SPF ?
September 14, 2008 10:33am CST
There are two systems for specifying a sunscreen's protection. American SPF numbers are double the SPF numbers on European products. An American SPF 20 sunscreen is the same as SPF 10 in Europe. Check which system is being used when you buy, and ask if you are in doubt. SPF is a laboratory measure of effectiveness. The European SPF system is based on the time a person with pale skin can remain in the sun without getting red and tender. This is usually 20 minutes in spring. If an SPF 8 sunscreen was applied, this would mean you could stay out in the spring sun for 8 x 20 minutes (160 minutes) without getting burnt. In practice, we don't know how quickly we burn, while factors such as sweat, water and application reduce sunscreen's effectiveness, so you shouldn't try to use this calculation as a guide. Application, application On a cloudy day 30 to 50 per cent of the sun's UV rays reach your skin, so it's still possible to burn. You may not feel the sun's rays if it's windy, but they still cause damage. Brief intensive sunbathing is harmful, eg all day in the sun for one week. It may contribute to skin cancer developing. On hot days use a hat and cover up arms and legs with loose-fitting clothes. If you want to avoid wrinkles and skin damage, the best protection is to stay in the shade. When out and about, a high SPF sunscreen offers protection, but its action will be limited if you skimp on application and forget to reapply. To get the most out of your sunscreen, follow these tips. Choose a 'broad spectrum' sunscreen. This means it provides UVA and UVB protection. It should have an SPF of at least 15 and at least four UVA stars. Apply sun lotion 30 minutes before you go out. Use a thick layer of cream to get the SPF protection indicated on the bottle. Even if you use a high SPF, you will burn if you miss bits and don't reapply frequently. The effect of sunscreen reduces after one to two hours in the sun – so make sure you apply more often than this. SPF 50 does not offer significantly more protection than a sunscreen with SPF 30. For this reason in Australia and America the highest SPF factor you will find is 30+. Swimming makes the skin more sensitive to the sun. Use a water-resistant lotion and always reapply sunscreen after swimming. Sweating dissipates sunscreen. If you sweat in the sun or you're taking part in any physical activity outdoors, make sure you reapply the lotion or use a cream that isn't absorbed by the skin. Look for products containing titanium dioxide or zinc oxide. Certain perfumes and creams can cause hypersensitivity to the sun's rays. To be safe, avoid wearing any products other than sunscreen when exposed to the sun. What are the warning signs that you've been out too long? Heat - your skin feels warm to the touch, even when you try to cool it with water. Reddening. Soreness. The reddening can be hard to see at first, but gradually becomes more obvious. You can test for this reddening: press your thumb against your skin lifting it will reveal a white area , if this turns red again quickly, you have spent too long in the sun. What can be done to relieve sunburn? Cool the sunburnt area in tepid water for 30 minutes to one hour. Apply a pain-relieving gel, calamine lotion or other soothing lotion. Ask your pharmacist for advice on products you can buy without a prescription.