A simple explanation of how Sun Protection Factor works

You may know Sun Protection Factor better by its acronym, SPF, and there’s also a good chance that you know that it is a measure of the protection you get from sunburn. Sunscreen brands use SPF to illustrate how much defence your skin has against UV rays, with the typical variants being 15, 30 or 50. But, did you know there are multiple types of UV rays, and that the difference in each level of SPF is huge?

This article will offer an explanation of how SPF works, so next time you’re applying your sunscreen, you know exactly what you’re protecting yourself against. We have discussed the importance of sunscreen in a prior article and we also offer a number of skincare treatments that use products with SPF to help against both sunburn, anti-wrinkling and anti-ageing, and these are worth checking out if you want even more information.

What is SPF?

An SPF number indicates how long it takes to infiltrate the skin and damage the DNA of your skin cells. One easy way of thinking about this is that the application of SPF 15 sunscreen means that it would take 15 times longer for the sun’s UV rays to reach your skin, compared to how long it would take if it was completely unprotected. SPF 30 would take 30 times longer, and so on. This is why it’s really important to reapply throughout the day, especially if you’re exposed to sunlight for large periods.

However, this doesn’t mean you have total protection against UVA and UVB rays for given periods of time. A sunscreen with an SPF of 15 only blocks 93%, with 30 blocking a substantially higher 97% and 50 blocking 98%. Products with an SPF of 100 manage to block 99%, but even with this high level of protection, some rays will still manage to pass through. Now, this might imply that the differences between SPF 30, 50 and 100 are rather minimal, but in fact, each is actually offering around 50% more protection than the last, so there is a significant difference between each.


Can you still sunburn with high SPF?

Whilst an SPF of 30, 50 or 100 can be extremely effective, they sometimes pose the risk of putting you into a false sense of security, and as a result, sunburn and the damaging of skin can sometimes still occur. It’s not unusual for people assume that one application of higher SPF sunscreens will be enough to see them through the day, but this is definitely not the case! Hourly reapplication of an SPF 15 sunscreen would prove much more effective than one application of an SPF 100 sunscreen. If you’re looking to enjoy a day in the sun, we’d always advise regular reapplication, ensuring that all of your body is protected, with a thicker coating on areas that are going to face more exposure (such as your arms or neck).

You want to be safe whilst enjoying the sun, so understanding how protected against its rays are is important, especially UVB rays, which are responsible for skin reddening and UVA rays, which are less intense but far more penetrating, and can be responsible for skin ageing and wrinkling. As well as the SPF factor, one should also take into account a products UVA star rating which ranges from 0 to 5, with 5 offering the highest level of protection against UVA rays.

Overall, we advise choosing a product with a minimum SPF of 15, and a UVA rating of at least 4 and continually reapplying it throughout the day. Doing so will go a long way in protecting your skin and ensuring you won’t suffer sunburn whilst enjoying the heat.

Each of our skincare experts here at AP Skincare has a wealth of knowledge gained from years of practical experience, so we’re able to give you tailored advice that’s unique to your needs and personal circumstances – whether that’s to do with sun protection, or our range of skincare treatments. Call into our Blackburn treatment centre today on 01254 297 000, or book an appointment to visit us in person – we’re always here to help!