SPF

SPF stands for sun protection factor. SPF is a number that represents how long a person can stay out in the sun without burning while using the product. It refers to the amount of ultraviolet energy required to produce a minimal redness or minimal erythema dose(MED) on unprotected skin. If a person normally burns in 10 minutes without sunscreen, an SPF-15 sunscreen will protect your skin for 150 minutes. However, there is no such thing as total protection from the sun, you will still get sunburn if you do not continuously reapply sunscreen while your skin is exposed to the sun.

You may start to think using a high number of SPF, you will never need to reapply sunscreen, but that simply isn't the case if you want to protect your skin. A higher SPF also means a greater concentration of chemicals, which can lead to a greater risk of allergic reactions.