what does spf mean and which one should you use?

We all know that using sun cream is a must in order to protect our skin against the negative effects of excessive sun exposure. Awareness of the risk of skin damage, and the desire to prevent the emergence of premature signs of ageing, has made us all more conscious of protecting ourselves against the sun’s UV rays. However, the SPF levels which are assigned to each sun cream product can be a source of confusion.

It’s essential to know exactly what you’re buying so that you’re aware of the level of protection you’re getting, so here’s our easy guide to understanding SPF.

What is SPF?

SPF stands for ‘sun protection factor’ , and is a number which indicates the level of protection a sun cream product provides against ultraviolet, or UV rays. Technically, it’s a measurement of the length of time for which a product can keep your skin protected from sun damage.

The SPF factor is generally intended to tell us about the level of protection against UVB rays, however in recent years there has been more attention to the impact of UVA rays.

UVA vs UVS rays

The sun produces two types of ultraviolet rays: UVA and UVB rays. UVB rays are the most commonly discussed. They tend to impact the outside layers of the skin, known as the epidermis. UVB rays are the cause of surface sunburn.

UVA rays can penetrate much deeper into the dermis, the lower level of the skin. These rays are the source of sun tan, but they are also associated with the development of lines, wrinkles and signs of ageing.

What does SPF 15/30/50 mean on the SPF scale?

The SPF scale is intended to tell you how long a product can protect against the sun’s ultraviolet rays, specifically UVB rays, so the factor should tell you how many times longer you will be protected compared to if you did not wear any sun cream.

Here's what each number of SPF means:

SPF 15: This level of SPF provides moderate protection by blocking approximately 93% of UVB rays. It allows you to stay in the sun 15 times longer than without sunscreen before getting sunburned.

SPF 30: This is a higher level of protection, blocking about 97% of UVB rays. It allows you to stay in the sun 30 times longer without burning compared to not wearing sunscreen.

SPF 50: This is the highest level of protection available commercially. It blocks approximately 98% of UVB rays, allowing you to stay in the sun 50 times longer than without sunscreen before experiencing sunburn.

What is the difference between SPF 30 and SPF 50?

If you wear a sun cream with SPF 30, you would expect to have about 30 times more protection than if you did not use it, and it will take you 30 times longer to burn. A sun cream with SPF 50 only allows 2% of UVB rays to penetrate your skin, compared to an SPF 30 product, which 3% of UVB rays can get past, meaning that 50% more harmful ultraviolet rays can reach your skin with the lower factor.

On some sun cream products you may find a star-based rating. Star ratings relate to the ratio of % UVA absorbed compared to UVB. So, Products are rated with 3 to 5 stars, with 5 stars being the highest ratio of UVA to UVB protection.

What is the best SPF for me to use?

The best sun creams and SPF products are those with broad spectrum protection, meaning that they protect against both UVA and UVB rays. Products with this quality are generally labelled to specify that they offer broad or full spectrum protection.

SPF products come in a number of different forms: creams, lotions, oils and sprays to name just a few, so you’ve got the choice of which kind of sun protection suits you best. For those with dry skin, a hydrating SPF lotion or cream will provide their skin with the moisture they need, while for those looking for a silky, luxurious feel, an oil may be their preferred choice. What’s most important to know is that the type of product you choose won’t change the level of sun protection it provides; so a sun cream with SPF 30 will protect you from sun damage to the same degree as a spray with the same factor.