40,000 people are diagnosed each year with skin cancer leading to 2000 deaths and the rate is set to double in ten years. Within this time, experts fear that the incidence of the disease could outstrip lung and bowel cancer to become the biggest cancer killer in Britain.
The main culprit of skin cancer is invariably too much exposure to ultra-violet radiation emitted by the sun. The UV radiation responsible for burning the skin can be divided into UVA and UVB rays. What’s the difference between them? A simple way to remember their effects on the skin is A for ageing and B for burning.
UVA rays penetrate deep into the skin’s dermis layer and repeated exposure causes long term effects which show as premature ageing (lines, wrinkles, age spots). Like B rays, UVA can also burn but much higher doses are needed and tanning occurs first. UVA are the main components of sunbed radiation.
UVB rays are absorbed into the upper layer of the skin and have the greatest tendency to produce sunburn. These rays are also emitted by sun lamps. Too much causes sunburn, freckles and skin thickening and a leathery appearance. UVB rays can lead to skin cancer.
Sunscreens work by reducing the amount of ultra-violet radiation that reaches the skin. There are three types of sunscreen available. The first is a mineral based physical sunscreen which reflects the UV rays away from the skin- such as titanium dioxide or zinc oxide. The second is a chemical sunscreen which protects the skin by absorbing UV rays. The third is a combination of the first two.
Chemical sunscreens can cause irritation in people with sensitive skin
All suntan preparations carry a S.P.F. number. S.P.F. stands for sun protection factor and is a measure of the sunscreens ability to protect against UVB. The higher the S.P.F. number then the more effective the product is at preventing the sun’s rays from reaching the skin and so the time you can spend in the sun increases.
A S.P.F. value of 5 means that it takes 5 times as long for the skin to burn compared to the time if you were wearing no protection at all. If you bum normally after ten minutes of sun exposure then a S.P.F. of 5 will allow you 50 minutes protection. The sun’s effect on the skin accumulates over time. And once you reach the end of the suntan’s protected time then the skin will bum. So with the above example, an application of factor 5 will give 50 minutes protection. A second application at the end of this time will not allow longer time in the sun – you will burn!
Manufacturers are also beginning to use a star rating system which measures the protection against UVA radiation. Four stars indicates moderate to maximum protection.
The terms water-resistant and water-proof are interesting. Water-proof means no loss of S.P.F. value after 80 minutes and water-resistant no loss after only 40 minutes.
