An Idiot's Guide to Sun Cream

Sunscreen is a must in the summer – we all know that but why? How does it work? What are the different types? What the hell does SPF even mean? Are we wasting money buying the expensive stuff or does it actually give you better protection? What’s the impact on our vitamin D levels? These are all questions that I have about sun cream, and I’m sure I’m not the only one, so I will try to answer them all in this Idiot’s Guide to Sunscreen.

What are the different types of sunscreen and how do they work?

There are two types – chemical sunscreen and physical sunscreen. You can also get hybrid products which contain both physical and chemical filters.

The two types protect us from the sun in different ways. Physical sunscreens deflect the sun’s rays whereas chemical ones absorb the rays. But how do we the difference? From experience I know that this is not always easy and you may have to look at the ingredients lists to find out. The active ingredient in physical sunscreens is usually Titanium dioxide(TiO2) or Zinc oxide (ZnO) and in chemical ones the list is a bit longer: Octylcrylene, Avobenzone, Octinoxate, Octisalate, Homosalate, Helioplex, 4-MBC, Mexoryl SX and XL, Tinosorb S and M, Uvinul T 150 and Uvinul A Plus. There is no way I could remember all of these when I’m in a shop trying to pick one so my tip would be that unless you can see Titanium dioxide or Zinc oxide in the ingredients list it’s a chemical sunscreen (source). The consistency of the product may also give you a clue about what type it is. Physical filters tend to be thick, opaque and leave a white tint whereas chemical filters tend to be colourless, odourless and runny. As far as I know physical filters currently cannot be used in sprays or aerosols so if it is a spray it's probably a chemical filter.

What does SPF mean?

SPF stands for sun protection factor and it is a measure of how long a sunscreen will protect you from UVB rays. The calculation depends on your skin type (source), and multiply the time for your skin type by the SPF, fair skin = 10 minutes, olive skin = 15 minutes, dark skin = 20 minutes. So for example, I burn but not very easily so I would go with olive skin. If my sunscreen is SPF 30 then the product will protect me from UVB rays for 7.5 hours (15 x 30). This calculation doesn’t apply to UVA rays (the ones that damage collagen and elastic tissue in the bottom layers of your skin but also cause you to tan – a response from your skin to the damage that has already been caused and an attempt to limit any further damage). It’s important to remember though that you will not be protected against 100% of UVB rays. Yes, the higher the SPF the better the protection but some rays will still get through.

Does sunscreen have a negative effect on our vitamin D level?

This is a big debate and with rickets making a comeback it is something many people are concerned about. In 2013 King’s College London carried out a study to find the answer to this question and according to them it’s a “no”. They found that the participants (whose baseline vitamin D levels were about 50 nmol/L and were thought of as adequate) despite using sunscreen still produced significant amount of vitamin D from sunlight exposure. Another study published by The British Journal of Dermatology (source) found that sunscreens can reduce the production of vitamin D under very strictly controlled conditions however their normal usage does not generally result in vitamin D insufficiency.

What’s available?

With the holiday season fast approaching this is the time to go out and buy sunscreen (not that we shouldn’t be wearing it all year round). I had a look through what’s on offer in Boots and compiled a list of the more popular products and some that you may not have heard of, how much they cost and which type of sunscreen it is. I also only included ones with SPF 30 or above because no one wants to be reapplying sun cream every hour ;) 

Garnier Ambre Solaire Protection Lotion SPF 30 200ml | Hybrid | £7.50

Garnier Ambre Solaire Clear Protection Water Resistant Spray SPF 50 200ml | Chemical | £7.50

Garnier Ambre Solaire Dry Mist Protection SPF 50 200ml | Chemical | £8.50

Nivea Sun Moisturising Sun Lotion SPF 50+ 200ml | Hybrid | £7

Nivea Sun Swim & Play Lotion SPF 50+ 150ml | Hybrid | £8.50

Soltan Adult Dry Touch Spray SPF 30 200ml | Chemical | £6

Soltan Face 8 Hour Sun Protection Moisturising Cream SPF 30 50ml | Hybrid | £4.50

Soltan Moisturising Suncare Stick SPF 30 5g | £4

La Roche Posay Anthelios XL Anti-Shine Dry Touch SPF 50+ 50ml | Hybrid | £16.50

La Roche Posay Anthelios Comfort Protective Oil SPF 50+ 200ml | Chemical | £18

No7 Protect & Perfect Intense Facial Sun Protection SPF 50 50ml | Hybrid | £14.50

No7 Protect & Perfect Intense ADVANCED Anti-Aging Sun Protection Spray SPF 30 200ml | Chemical | £14.95

Vichy Ideal Soleil Face & Body Milk SPF 50 300ml | Hybrid | £14.25

Vichy ideal Soleil Mattifying Face Dry Touch SPF 30 50ml | Chemical | £12.37

Should we be using sunscreens all year round?

Yes. UVA rays are present all year round meaning we might not necessarily tan however it can cause damage to the superficial layers of the skin.

Destabilisation

The majority of chemical filters will destabilise due to a variety of factors within a couple of hours of application. This means we are not getting the sun protection that we think we are. Not all chemical filters are photo-stable (most sunscreens use a few different ones in their products) meaning that being out in the sun decreases the length of time they protect us for. Another common factor that contributes to sunscreen destabilisation is the application of other products, e.g. make-up. This is where physical filters are better than chemical ones as they tend to be more natural and don't destabilise anywhere near as quickly as the chemical filters.

The sunscreen debate could go on for days but I hope this post answers at least some of the basic questions and makes it clear what you should be looking out for when buying sun cream.