Is there ANY point in buying Factor 50? Many products are a waste of time and money There's nothing like a heatwave to put a smile on the face of the sun cream manufacturers. After a run of soggy summers in which bottles of Soltan, Ambre Solaire and Piz Buin have gathered dust in bathroom cabinets, millions of us have hit the High Street in search of sun protection. In recent years, manufacturers have unleashed an extraordinary range of products on the public - often at extraordinary prices. Some are said to last for eight hours or are water resistant. Others boast you can stay out in the sun 50 times longer than normal without burning. But, according to skin experts, many of these products are a waste of time and money and their claims are virtually meaningless. Crucially, the difference between high factor creams such as 30 and 50, and factor 15 is minimal in terms of sun protection. And it makes almost no difference if you only spend a few hours in the sun. Some even argue slapping on the highest factor creams could cause us to be reckless with sun safety. And remember, all creams will still let some burning rays through. So what should we be using to protect against sunburn, skin cancer and an old age of leathery, wrinkly skin? And how do we avoid being ripped off? Despite health messages about skin cancer - which kills more than 2,200 people annually - one woman in four doesn't use sun cream, while one in three uses lotions that are a lower factor than 15. A tan is not a sign of a healthy body, but an indication skin has been damaged by cancer- causing ultraviolet, UV, rays. Caucasian skin gets a golden colour from the pigment melanin. When skin is damaged by UV rays, it produces more melanin in self-defence. The risk of cancer is highest for those with white, freckly skin who never tan. It is lower for people with a Mediterranean complexion, and lowest for those with black skin. Ultraviolet radiation has two forms - UVA and UVB. The latter is the main culprit for sunburn and skin cancers. But UVA can also increase the risk of cancer and cause premature skin ageing. Each year there are 70,000 new cases of skin cancer and doctors say the disease is preventable in four out of five cases. Yinka Ebo, of Cancer Research UK, says: 'You should avoid sunburn because it is a sign the DNA in skin cells has been damaged by too much ultraviolet. A painful sunburn once every two years triples the risk of skin cancer. Two ingredients in creams protect the skin. Some are 'absorbers' that mop up harmful UVB rays. Others are a physical shield and reflect them. These often contain zinc oxide or titanium oxide. Both increase the amount of time you can spend in the sun without burning. All creams wear off, so must be reapplied every few hours. SPF stands for sun protection factor. Dermatologists say it should stand for sunburn protection factor, as it only refers to how good the cream is at protecting against UVB, the rays that cause sunburn. Few of us spend 12 hours in the sun and factor 30 would give 7½ hours burn-free. If you spend only a few hours in the sun, whether you wear factor 15, 30 or 50 will make little difference No matter what your SPF factor, it is crucial you reapply your cream every few hours. A cream with an SPF of 15 means you can stay in the sun for 15 times longer than you could with no sun cream without getting burnt - as long as you have it on thick enough and keep reapplying it. So, if you start to redden after 15 minutes, a cream with an SPF of 15 should allow you to stay out for 225 minutes, or 3¾ hours, before you burn. This is the case no matter how many times you reapply it. After 3¾ hours, the only safe solution is to find shade. An SPF factor of 30 allows you twice as much time in the sun as a 15 - but should be reapplied every few hours. So, an SFP 30 should let you enjoy 450 minutes or 7½ hours without burning. After that you can reapply as much as you like and it won't protect you. If you burn after 15 minutes and plan to spend 12 hours in the sun, factor 50 should let you do so without burning. Reapplication is crucial. But as few of us spend 12 hours in the sun and factor 30 would give 7½ hours burn-free, factor 50 is probably not worth it. If you spend only a few hours in the sun, whether you wear factor 15, 30 or 50 will make little difference. The risk of cancer is highest for those with white, freckly skin. It is lower for Mediterranean complexions And doctors recommend we avoid long periods in the sun, as the rays can still damage our DNA without sunburn. Experts say the SPF system is misleading when it comes to how much of the sun's harmful rays different factors absorb. An SPF 2 cream absorbs 50 per cent of harmful rays, while an SPF 8 absorbs 70 per cent. But as the numbers increase, the additional benefit gets smaller. A factor 15 cream absorbs 93 per cent of UVB; factor 30 absorbs 97 per cent; and factor 50 absorbs 98 per cent. So, there's very little difference in how much UVB factors 15, 30 and 50 block out. Nina Goad, of the British Association of Dermatologists, says: 'There are concerns sunscreens offer a false sense of security. Using a very high protection cream, such as 50 or above, does not offer you double the protection of a product with half the SPF. SPF only describes the ability of a product to filter UVB. To see if a cream or spray protects against UVA, look for a separate star rating. The stars go from zero to five. These show how much UVA radiation is absorbed by the cream compared with UVB. So if an SPF30 cream has five stars, it offers the same high protection against UVB and UVA. But if an SPF8 cream has five stars, it offers the same low protection against UVB and UVA. Critics say the star rating is a marketing ruse, not sensible medical advice. Most people don't put on nearly enough and don't reapply it often enough. SPFs are worked out on the assumption people smear a layer of 0.025g for every two centimetres of skin - 35ml for a whole body, or two large tablespoons. For the arms, neck and face you need at least two teaspoons. It needs to be fully absorbed by the skin. You must apply it 15 to 30 minutes before going out and a second coat 20 to 30 minutes after you've been in the sun. If you are out all day, you will need two or three smotherings. A typical bottle contains 200ml - six applications. For a fortnight's holiday in the sun, two adults and two children need 21 bottles. Every cream on sale in Europe must do what it says on the label by law. What you are paying for with the most expensive brands is smell, consistency and name. But you're not risking your health with a cheaper, own-brand name. Creams should have a best before date. After three years, they won't offer anything like the same protection.