There are so many lotions, sprays and oils available that claim to protect you from the sun that looking at the rows of sunscreen products in shops can be a baffling experience. It can be difficult to know which one to trust, and with skin cancer second only in occurrence to lung cancer in the UK, it is important that an educated decision can be made. People with moles are very vunerable to skin cancer, and need to be very careful in the sun. Moles that itch, or change size, colour or shape should be checked by a doctor.

Explaining the Jargon

Sunscreen needs to have UVA and UVB protection to really work. UV stands for ultra violet, the 'colour' of the invisible rays that make up part of the sun's energy that reaches earth. UV rays enter body cells, causing visible and invisible damage. The visible damage takes the form of sunburn, freckles and a tan. Invisible damage can be repaired by the body, but the build up over a decade or two can cause wrinkles, age spots, and cancer.

UVB rays are the ones that burn your skin, UVA rays are the ones that cause deep down damage. Sunscreen that blocks out both these types of rays is essential for keeping your body healthy in the sun.

Some sunscreens state that they protect from IR. This stands for infra red, the 'colour' of the rays that cause the sun to feel hot.

SPF stands for Sun Protection Factor, and mainly applies to UVB rays¹. Followed by a number, this is the amount of protection that the sunscreen will give. The time that it will protect can differ from person to person. SPFs work on the principle that if it takes a person 15 minutes to burn in the sun with no protection, then a SPF of two would protect for two times 15 minutes. An SPF of 30 would protect for 30 times 15 minutes, giving 450 minutes or seven and a half hours protection. However, this protection also depends on a number of things:

• Sunscreen should be applied at least 15, and preferably 30 minutes before you go out into the sun. This gives it time to be absorbed into your skin and start working.

• Sunscreen must be spread thickly. At least one teaspoon per arm, one for the body, and two for each leg.

• Swimming will wash off sunscreen eventually², so it will need to be reapplied after going in the water. Towelling dry will also remove all sunscreen.

• Sunscreen must be reapplied at least every two hours to stay effective.

• It may be wise to mix and match, with a higher SPF on the more vulnerable parts of the body, such as the face, elbows and knees.

Remember that once the time is up, it's up. You don't get another seven and a half hours by reapplying the cream.

PABA-free refers to an absence of Para Amino Benzoic Acid. This is a B-complex vitamin that can be synthesised by the body, and blocks UVB rays. Unfortunately it can cause a stinging or burning sensation in some people, and a bad rash in others, particularly when used on the face. Non-PABA sunscreens use chemicals less likely to cause irritation to block UVB rays.

Sun Block

There are two kinds of sunblock, invisible and visible. Most sunblocks only contain the invisible, although those made for children are likely to have both. The invisible is the kind of chemicals that trap the UV rays and prevent them from entering the skin. The visible is a physical barrier containing zinc oxide or titanium dioxide. This means that the cream will stay visible on your skin and is normally white, although coloured ones are available.

Coloured sunscreen is a good idea for children, as it enables you to see if any bits have been missed. Some are designed in bright colours that fade once the children are out in the sun.

Danger Zone

• If your shadow is shorter than you are, you are at risk from the sun. Try to stay in the shade.

• Fair skinned people can burn in as little as 15 minutes at midday.

• Babies under six months should not be exposed to direct sunlight. If it is unavoidable, a SPF 15 sunscreen should be used.

• UV rays pass through clouds, so even on overcast days, you still need protection. Water, sand, snow and other surfaces reflect the rays back onto your skin, and can be more powerful than direct rays.

• UVA rays can pass through glass, although UVB rays are blocked. Both can pass through water.

• Some medicines such as antihistimines, antibiotics, birth control pills and antidepressants can increase sensitivity to the sun. Check the information leaflets that accompany any medicines, and act accordingly.

Fascinating Facts

• The SPF system was introduced in 1978 by the American Food and Drug Administration, when the highest number was 15. By 1986, the highest factor was 20, but this has kept on rising.

• SPF 15 gives 95 percent protection from the sun. SPF 30 gives another two percent. With each increase the amount of protection gained grows smaller. An SPF higher than 30 is a waste of money.

• More expensive doesn't mean better protection from the sun, although there may be other benefits.

• 'Water resistant' sunscreens will last approximately 40 minutes in water. 'Very water resistant' will last 80. The FDA are considering disallowing the use of the word 'waterproof' in reference to sunscreen.

• Most accumulated damage occurs before the age of 18. Keep children protected to avoid problems in the future.

• A dark tan on white skin will only offer protection of about SPF 4. It is worthwhile remembering that tanned skin is already damaged.

• Gel based sunscreen is better for people with oily skin, or who are sweating. Cream is best for dry skin, and lotion for normal skin. Sprays aren't recommended, as although they are sold as the easy option, they are difficult to apply evenly, and it's more difficult to know when you've applied enough.