We all know that wearing sun protection daily (all year round) is the best sure-fire way to delay the ageing process.
But what does SPF mean? And what do the numbers stand for?
The term SPF stands for Sun Protection Factor, and the number which follows relates to how many more times somebody can be exposed to UV rays for before they burn. It is tested in-vivo (on humans) by exposing two small patches of skin, one with product and one without, and seeing how long each takes to show erythema (skin redness). The ratio between these two times then gives you your SPF value. e.g. if it takes 15x longer for the treated patch to burn vs, untreated, that would give you an SPF15.
But SPF is only half the story.
SPF specifically relates to UVB rays, which are not the only wavelength the sun exposes us to. UVA make up another part of the sun’s rays, so how do we protect ourselves from them? Chemical-based sun protection products in Europe use a blend of filters to cover a broader spectrum of UV rays. Legally, in the EU, a product must have at least 1/3 of the protection of UVA to UVB in order to be legally sold as a sunscreen.
So an SPF30 needs to have at least a UVA protection of 10. This is much more difficult to measure in vivo, as UVA rays do cause the same instant effect as UVB in the form on sunburn. That’s not to say they do not cause damage over time – in fact they are thought to have an even greater effect in the skin-ageing process than UVB.
So are all sun protection products created equal?
Not exactly. There are two types of sun filters which you can find in your products. On is a physical filter, either zinc oxide or titanium dioxide, which forms a layer on top of the skin, and effectively reflects the UV light away so it cannot penetrate the skin and cause any damage. This type of filter does not get used up in the process, but merely acts as a protective all over shield, blocking all wavelengths of UV light.
Sounds great, right? The problem is the experience of this type of product, which can be very white and hard to run in (think a cricketers sunblock – this is in fact zinc oxide paste). Incidentally, titanium dioxide is used in a wide range of colour cosmetics and will most likely be the material providing the SPF in your foundation. It’s also why make-up artists steer clear of any base with SPF as this will reflect any type of light, which can cause flashback in photos.
The other type of sun filter is chemical.
These filters are designed to absorb into the skin, then dissipate any harmful UV energy that penetrates the skin by converting it into heat energy.
Formulas tend to be much more lightweight and invisible, providing a much better experience, but there are a couple of cons here too.
Firstly, they tend to wear off more easily throughout the day, as the filters are used up in the process of converting the UV energy into heat, so you need to be especially cautious on re-applying if you are outside in the afternoon.
Secondly, certain common chemical filters can be irritating to more sensitive skin types, so if you have more reactive skin you may be better off with a mineral formula.
So we hope that gives a little snippet into the behind the scenes world of sunscreen.
See below our pick of the bunch:
Heliocare 360 Mineral Tolerance - my most commonly recommended - best for all round, fragrance free mineral protection
Heliocare 360 Gel Oil Free - chemical based, but oil free, this one is great for oilier or blemish-prone skin types
Organii Everyday Organics SPF50 Sun Milk - mineral-based filters, and free from silicones and fragrance, this formula is great for those who are looking to avoid synthetic ingredients
La Roche Posay Anthelios SPF50 - great affordable option, chemical filters, hypoallergenic, fragrance free formula