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Health
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SPF
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Sunscreens
Melanoma
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SPF
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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