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Sun Protection Factor

Sun Protection Factor (SPF) The very first system to rate the effectiveness of sunscreens used SPF numbers. The idea is, how long it takes for someone's skin to go red when a sunscreen has been used, compared to someone without using a sunscreen.

If you were to be exposed to the sun with a sunscreen with a SPF 15 rating, you would not go red until you had been exposed for 10 X SPF 15 = 150 minuets. ' (Don't try this at home warning) These numbers were produced experimentally with the use of sunlamp, with and without the sunscreen, these tests are for UVB not UVA. It took many years for sunscreens to cover UVA.

Today we are told that the higher protection (SPF rating) the better the sunscreen, and the more it protects against UVB the more it should protect against UVA.

In the UK we also have a star rating, that allows us to compare two products with the same SPF rating but different levels of UVA protection. At any SPF level, the products with the greatest UVA protection get 5 stars, those with somewhat less, 4 stars etc.

Category label SPF rating label Actual measurement Minimum UVA protection factor
Low 6 6 – 9.9  
Must be no less than 1/3 of the labelled SPF rating (column 2)
10 10 – 14.9
Medium 15 15 – 19.9
20 20 – 24.9
25 25 – 29.9
High 30 30 – 49.9
50 50 – 59.9
Very High 50+ ≥60

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