Sunscreens are skin creams, lotions, and sprays designed to minimize the risk of sunburn by reducing the amount of UV radiation reaching the skin. Sunscreens also significantly reduce the risk of photo ageing and skin cancer if used properly. Sunblock refers to more powerful sunscreens. Sunblock tend to be white creams containing zinc and titanium oxide that reflect most of the sunlight, however they still let some UV radiation through.
There are three types of sunscreen : sunscreen containing organic chemical substances that absorb UV radiation, sunscreens containing fine inert powders that largely reflect UV, and combinations of those two.
SPF stands for Sun Protection Factors. SPF indicates the level of protection against sunburn from UVB. Sunscreen SPF rating is calculating by comparing the amount of time needed to produce sunburn on sunscreen protected skin to the amount of time needed to cause sunburn on unprotected skin. SPF number can range from 2 to greater then 50. SPF 25 gives better protection against UVB than SPF 15. For example : person who normally turns red after 10 minutes under sun exposure without sunscreen, when she applies SPF 15 sunscreen on her skin, it would take 150 minutes for her skin to turn red. But better reapply sunscreen every two hours for continued protection.
The star rating (* to ****) indicates the degree of UVA protection, The more the stars, the better the sunscreen protection provided. However, exact UVA protection is not easy to measure.
When you choose a sunscreen, select products with good sun protection qualities, indicates by the SPF number and the star rating. If you intend to go swimming, you should check that your sunscreen is water resistant. Sunscreens should be re-applied at least every two hours or after swimming or perspiring heavily. Water-resistant sunscreens may lose their effectiveness after 40 minutes in the water. Don’t forget to reapply sunscreen after you have towel-dried.
