UVA and UVB rays are the rays responsible for burning and aging our skin when we've been over exposed to UV radiation. So we wear sunscreen to shield our skin from this damage that is both visible and non-visible to the naked eye.
We all know our beloved sunscreens that we've been wearing since childhood, come with an SPF rating. But what does it actually mean? And what does it tell me about my sunscreen?
SPF Meaning
SPF stands for sun protection factor, which is a measure of how well sunscreen protects against UVB (ultraviolet B) rays. However, protection from UVA (ultraviolet A) rays is signified via a broad spectrum label.
The SPF of a product is provided by one or more UV filters (there are 33 approved in Australia). These work in conjunction with other actives in a products formula to further enhance your consumer experience and provide additional product benefits.
To figure out anything's SPF, divide the length of time it takes to burn without sunscreen by the length of time it takes to burn using the sunscreen. For example, if you normally burn after 10 minutes of sun exposure and you use a sunscreen with an SPF of 15, you can stay in the sun 15 times longer -- about five hours -- before burning.
SPF stands for sun protection factor, a measure of how well sunscreen protects against UVB rays. (UVA protection isn't rated.) Manufacturers calculate SPF based on how long it takes to sunburn skin treated with the sunscreen as compared to skin with no sunscreen.
Experts recommend using a sunscreen with an SPF of at least 30. Sunscreens with SPFs greater than 50 provide only a small increase in UV protection. High-number SPFs last the same amount of time as low-number SPFs.
Sunscreen is often not applied thoroughly or thickly enough, and it can be washed off during swimming or sweating. As a result, sunscreen might be less effective than the SPF number suggests.
In Summary
Simply put, SPF measures a sunscreen’s ability to protect you from the sun’s burning rays. In theory, SPF 30 prevents 97% of UVB from reaching your skin. Theoretically, this means you could stay in the sun 30 times longer before getting a sunburn than if you went without protection. But there’s more to it than that.
Find out how to pick the best sunscreen for your face here.