Most of the damage from the sun comes from UV (ultra violet) rays - UVA and UVB.
UVB rays penetrate into the outer layer of the skin and damages the cells resulting in inflamed skin or sunburn.
UVA rays penetrate more deeply causing direct damage to the skin's supporting tissues, which contributes to the signs of skin ageing.
Therefore, we need to be protected against each of these types of UV rays. This section shows how sunscreen helps protects us from harmful UV rays of the sun and why we can be confident in the protection labelled on-pack.
What are the different types of UV filters?
The key ingredients of sunscreens are UV filters. Their job is to help cut down the amount of ultraviolet (UV) rays reaching the skin.
They typically fall into two main categories:
synthetic or organic filters, which absorb UV light; and
mineral or inorganic filters, such as titanium dioxide, which mainly reflect UV light.
Because different UV filters tend to be effective against different wavelengths of UV, most sun protection products include filters for both UVA and UVB. This means they provide a broad spectrum of protection across the whole range of UV rays.
What is SPF?
Understanding SPF is simple. The higher the SPF number, the greater the protection the sunscreen will give.
SPF stands for Sun Protection Factor and is provided on-pack as a number. It is an indication of the amount of protection sunscreen provides against UVB rays. UVB rays penetrate the outer layer of the skin and damage the cells resulting in inflamed skin or sunburn.
The SPF number is easily recognisable as it is standardised throughout the UK, Europe and across most of the world. The higher the number, the greater the protection; but we shouldn't think of the SPF number as indicating multiples of the amount of time we could stay out in the sun without sunscreen before we burn. Sunsafe behaviour means we should not use sunscreen to stay in the sun longer.
The UV filters that provide the SPF in a sunscreen help to filter out UVB rays. An SPF of 15 will filter out approximately 93% of UVB rays and an SPF of 30 will filter out around 97%. While this might not seem like a big difference, it can have a significant improvement in sun protection for someone who burns easily. SPF15 is the recommended minimum by most health experts.
Alongside the SPF number there will be an indication of the type of protection the sunscreen offers - i.e. low, medium, high or very high.
The SPF numbers you are most likely to see now are shown in the table below.
The European Commission's Recommended SPF Numbers and their Protection Categories
The science behind SPF
Everyone reacts to the sun in their own way. Some people's skin is affected more by the sun's harmful rays than others. The SPF of a sunscreen it is measured by testing it in a standard way on a range of people to take this into account. This international standardised test provides an SPF number.
In the test, the set amount of product is applied to a measured area of skin on a number of people who are exposed to a specific amount of sunlight. The reaction of their skin is then assessed. But cosmetics companies don't just rely on just one test for the SPF number. During development, the product is tested by scientists a number of times to check the SPF is on track.
By the time the product has reached the point of the final SPF test on human volunteers, it has already been tested by scientists a number of times to ensure consistent results are seen.
This robust development and testing process is what companies go through before they label their product and put it on the shelf. So we can be confident the level of protection on the pack is correct.
Dr Emma Meredith, Director General of CTPA, explains what affects how sunscreens work and how to choose the right sunscreen for our skin type.
The SPF we should use will depend on our skin type. Skin specialists use a particular tool called the "Fitzpatrick Scale":
Identifying our skin type will help us to decide on the level of protection necessary during sun exposure. For example, skin type I requires very high protection since the body is less able to protect itself and the skin is readily burnt by small amounts of UV rays. Experts at the British Skin Foundation and British Association of Dermatologists are aware that we tend to under-estimate the sensitivity of our skin to sunlight.
When choosing a sunscreen we should aim for one that suits our skin, but with at least SPF15 or greater, which contains UVA protection, is water-resistant and has an application method that suits our needs; this will encourage proper usage. It is important that we follow all of the instructions for best protection, but remember sunscreen should never be used to stay in the sun for longer.
A person's skin type is the same over all the body, so the same SPF can be used all over. However, particular care needs to be taken over areas that are not usually exposed to the sun e.g. the abdomen, tops of the legs and the feet, or are particularly vulnerable to sunburn such as the nose, chest, tips of the ears and even the soles of the feet.
Although UVA rays do play a small role in sunburn, the main concern is that UVA rays penetrate deeper into the skin and cause damage to the cells resulting in premature skin ageing. Both UVA and UVB rays are attributed to causing skin cancers of several kinds.
The UVA protection that a sunscreen provides will be evident on the label. In the UK and across Europe, UVA protection is indicated on-pack by showing the letters "UVA" in a circle.
The UVA logo is used throughout the UK and Europe to show that a product contains at least the recommended minimum level of UVA protection for a sunscreen.
Whilst the star system to indicate UVA protection has been effective in educating consumers in the UK, it is a commercial labelling system and not all sunscreens in the UK will carry the star rating for UVA protection and they will not be used in other European countries or across the world.
The European Commission recommends that we should always choose a sunscreen that provides both UVA and UVB protection.
What's on a sunscreen label?
UVA protection and SPF levels are displayed clearly on sunscreen labels across the UK. There is a standardised way that sun products are tested and labelled throughout Europe. This means that in whatever country we buy our sunscreen, we'll be able to choose the UVB and UVA protection we want with minimum confusion.
Dr Emma Meredith (Director General of CTPA) and Dr Chris Flower (Former Director-General of CTPA) explain how to understand your sunscreen label.
How do sunscreens work?
The main component of a sunscreen product is the UV filter or filters. Their job is to help cut down the amount of ultraviolet light reaching the skin. UV filters can do this in one of two ways: they can either absorb the UV-light by 'soaking it up'; or they can scatter it and reflect it away from the skin. Consequently, there are two different types of UV filter and these are: absorber filters and reflector filters.
What are absorber filters (or organic filters)
Absorber type UV filters work by absorbing ultraviolet rays much like a sponge soaks up water. Each tiny sunscreen 'sponge' soaks up ultraviolet rays, and then releases it back out after converting it into lower energy and less dangerous infrared rays. These filters can be thought of as 'energy converters', converting dangerous UV rays into safer infrared warmth.
What are reflector filters (mineral or inorganic filters)
Unlike the absorber-type UV filters, reflectors tend to be less specific about the type of UV rays they reflect and tend to protect against both UVA and UVB. These sun filters act in a different way. Instead of soaking up the UV rays in the way that the absorber sun filters do, these materials reflect and scatter the UV rays away from the skin without changing it to anything else. They can be thought of as thousands of tiny mirrors each reflecting UV rays away from the skin.
Organic and mineral sunscreens - Is one better than the other?
No - they just work in different ways.
The most commonly used UV filters are the absorbers because these are more efficient (you get more sun protection for the same amount of ingredient). However they are often supplemented with reflectors.
Some people with sensitive skins or certain allergies may prefer a product with less absorber-type (organic) filters. In order to ensure that the product still provides the required amount of UV-protection, the absorber filters are replaced with reflector (mineral) sunscreens. Allergy and reaction to sunscreens are very rare so most users find absorber-type sun filters suit their needs.
There is a legal requirement that all cosmetic products, including sunscreens, must undergo a very strict safety assessment by a qualified safety assessor. The assessment covers the safety of the finished product, as well as all of the individual ingredients, how and where the product is to be used, by whom and how often.
Because different UV filters tend to be effective against different wavelengths of UV, most sun protection products include several different UV filters. This means they provide a broad spectrum of protection across the whole range of UV rays. Including different filters in a product also helps to achieve the high levels of sun protection.
Many sun filters will not dissolve in water and so many sunscreens will contain oil ingredients to help dissolve those sun filters. Manufacturers try to keep the oil content to an absolute minimum to prevent the finished product from being greasy, but a small amount in the product is essential.