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What Is SPF 50?

By B. Chisholm
Updated: May 17, 2024

SPF 50 stands for Sun Protection Factor 50 and is a measurement of the strength of sun cream. Overexposure to sunlight is one of the leading causes of skin cancers worldwide and the use of sun cream whenever a person is exposed to sunlight can go a long way in minimizing this risk. The number following the SPF – 50, in the case of SPF 50, is a measure of how much UV radiation is blocked by the cream.

Sunlight is broadly divided into two types of ultraviolet (UV) radiation, namely UVA and UVB. It is mostly UVA radiation that reaches earth. While UVB radiation is the type that causes most sunburn, both UVA and UVB can cause it.

When sunscreens were initially produced they aimed mainly at reducing UVB exposure. Newer sunscreens now include ingredients which reduce exposure to UVA as well and it is advised when buying sunscreen to check that they protect against both UVA and UVB. While exposure to the sun is important to obtain vitamin D, it should be done responsibly, to avoid the risk of sunburn and resultant risk of cancer.

When establishing the SPF factor of a sunscreen, that is whether it is SPF 5 or SPF 50, or anything in between, tests are conducted in the lab on humans. The number is calculated by working out how much longer a person can stay in the sun when applying the cream versus not applying it. SPF 30 will block 97% of UVB rays. SPF higher than 30 doesn't give significantly more protection. SPF 50 will block about 98%.

Choosing the correct sunscreen should involve the consideration of numerous factors. These include natural skin tone, expected exposure to sun and at what time, and ease of application. It should also be remembered that, to be effective, sufficient sunscreen should be applied and it needs to be repeatedly applied throughout the day, especially if swimming or sweating.

There are numerous makes and strengths of sun protection products from creams to sprays. Also available is makeup with SPF which is a good idea as it is applied daily when makeup is put on. Often makeup is not as high as SPF 50 so it should be checked that the sun protection factor is high enough for the expected sun exposure.

Extreme care should always be taken in the sun. Not only should sunscreen always be applied, but hats and protective eye wear should also be worn. Exposure to midday sun should be avoided, especially by those with fair skins. Even the highest sun protection factor sunscreen does not keep 100% of harmful sun rays out.

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