Summer Skin: SPF Explained
With the nice weather starting to hit, many of us are looking at picking up some sun cream to protect our skin during the summer months. But there’s so much choice! Selecting the most appropriate SPF for your skin is essential for minimising the risk of burns and blisters, but what exactly does SPF mean, and what’s the right SPF for your skin?
What is SPF?
The ‘Sun Protection Factor’ system was created in 1974, and it’s now the most widely used system for determining the level of protection offered by sun creams. Sun cream is typically available in factors of 2 all the way to 100, with numbers indicating what fraction of the sun’s UVB rays are let through to the skin when the sun cream is applied properly. For example, an SPF 15 sun cream will allow 1/15th of the rays through. What this means is that an SPF 15 sun cream provides 15 times the protection of bare skin.
What SPF do I Need?
It’s impossible to say exactly what fraction of rays are damaging (although the NHS does recommend SPF 30+ for optimal protection), and that’s because everyone’s skin is different. There is no ‘perfect’ SPF for everyone. Instead, finding the right SPF is about understanding the way your own skin behaves in sunny environments. For example, if you have very fair skin and usually start to burn after just 10 minutes, an SPF 15 sun cream would, in theory, allow you to safely spend 2.5 hours (15 times as long) in the sun.
We say ‘in theory’ because sunscreen usually needs to be reapplied after around 2 hours, especially if you’ve been swimming, or if you’ve been sweating in the heat.
2 Kinds of Sun cream
If you’ve been looking at your options, you’ve probably noticed that there are two types of sun cream available: physical sun cream and chemical sun cream. The most important thing to know is that SPF is SPF, no matter what type of sunscreen you choose. However, it never hurts to learn more about the differences between the two options:
- Chemical sun cream works by absorbing the sun’s UVB rays and transforming them into heat energy which can then easily be discharged from the body.
- Physical sun cream works by reflecting the sun’s rays away from the surface of the skin. This type is less common in the UK but it’s certainly not difficult to find.
As long as you choose the right SPF for you, it really doesn’t matter if you choose chemical or physical sunscreen. Physical tends to be thicker and goopier, while chemical sunscreens often come in lightweight variants such as dry sprays and oils. However, chemical options can be more damaging to delicate skin, especially if they contain alcohol. If you have sensitive skin on your face and chest area, use a physical sunscreen here, and use easier-to-apply, cheaper chemical options on the body.
Protection from UVA rays isn’t covered by the SPF system, but there are standalone systems that tell you how well a sun cream is at keeping UVA rays at bay. The Boots star system is most recognised here in the UK, with a rating from 1 – 5, 5 being the best. The NHS recommends choosing a sun cream that has at least a 4 star rating for UVA rays.
If a sun cream doesn’t have a UVA star rating, don’t worry! Some products use the EU system, so instead look for ‘UVA’ in a circle which shows it meets EU standards.
Keep it Fresh
Just because you’ve found an SPF sun cream in the back of your bathroom cabinet doesn’t mean you should use it. It’s important to remember that the Sun Protection Factor diminishes over time, with an average lifespan of between 2 – 3 years. Always check ‘Use By’ dates, and pick up some new sun cream when you need to.