Sun Protection Factor

SPF-15+ sunscreens filter out about 93% of UVB rays.
SPF-30+ sunscreens filter out about 97% of UVB rays. They are not twice as good.
Broad Spectrum sunscreens filter out at least 90% of the UVA rays as well.
How well they work also depends on other things such as skin type.

Some UVB rays always get through to the skin even with sunscreens, so sun damage can be happening if you stay in the sun a long time, even if you are using sunscreens.

Which sunscreen should you use?

Any brand which states SPF-30+ and has been tested will give good protection. Cost does not show how well a sunscreen will work. Lotions and gels tend to be drying and can irritate the skin, however they may be better for people with oily skin as creams may make acne worse. Allergy to sunscreens is now unusual, because the chemical which caused most allergic reactions (PABA) is now rarely used.

If one brand irritates the skin another brand may be fine. Changing the type of sunscreen usually stops any irritation. Sunscreens labeled for babies or toddlers generally have a gentler base and no perfumes, and may be less likely to cause problems. A water resistant sunscreen should be used if what you are doing is likely to cause heavy sweating or if you will be going in the water. Zinc cream can be used to totally block the sun (it needs to be spread quite thickly). It can be used on small parts of the body (e.g. the nose and the tops of the ears).

How to use sunscreens

Sunscreens should be put on clean, dry skin 20 minutes before you go into the sun. You need to use enough to easily cover any skin which is not covered by clothing. Apply generously – as a guide for an adult apply about one teaspoonful to each arm and leg and half a teaspoonful to the face, ears and neck. Less would be needed for a child. Sunscreens should be re-applied about every 2 hours to replace any that has been lost (eg. by blowing the nose, sweating, brushing against something).

Looking after sunscreens

Sunscreens last between 2 and 3 years, and the use-by date must be shown on the label. Sunscreens may not work well if they are left in the sun, in a hot place (such as in a car) or if the cap is left off.

Sunscreens and babies

Keep babies indoors as much as possible during high risk times such as the middle of the day. When babies are outdoors, use shade and clothing such as hats and long sleeves to keep the sun off. A baby's skin is thin, and does not have much natural protection from the sun, so it burns and gets damaged much faster.

Babies under 12 months do not need to be out in the direct sun. They will get all the sunlight they need for healthy development from reflected sunlight, eg if they are outside in the shade. Sunscreens appear to be safe for babies and should be used rather than risking sunburn. Sunscreens labelled for toddlers and babies contain the same sunscreen chemicals as ones labelled for adults, but usually have a gentler base and no perfume. If any product causes a skin reaction though, stop using it and try another one.

Use sunscreens only on the small areas of the skin which cannot be protected by shade and clothing, such as the baby's face and hands. Remember that sunscreen rubbed into the eyes can make them very sore.

Zinc cream can be a good sunscreen for babies.