When purchasing sunscreen you may have noticed different numbers of the SPF.
But what is SPF?
SPF means sun protection factor.
The sun protection factor is a relative measure of how long a sunscreen will protect you from ultraviolet (UV) B rays.
SPF 30 is the most common level for most people and skin types. No sunscreen can block all UV rays, but what we do know is: SPF 15 blocks 93% of UVB rays, SPF 30 blocks 97% of UVB rays and SPF 50 blocks 98% of UVB rays. So, the difference between 30 and 50 is about 1 percent.
The chief cause of reddening and sunburn, UVB rays tend to damage the epidermis, skin's outer layers, where the most common (and least dangerous) forms of skin cancer.
You should always wear an SPF of at least 30.