With so many sunscreen products on the shelves nowadays, some boasting SPFs as high as 130. You may have also noticed that some of them carry a PA notation after the SPF value, like SPF15·PA++. So, what is SPF and what is PA? And learn why higher SPF isn't necessarily better.

How Sunscreen Works

The ingredients in sunscreen protect the skin by absorbing, blocking or scattering UV radiation. The best sunscreen is the one that blocks enough UV rays to protect your skin. For the best results, apply sunscreen 30 minutes before exposing to the sun.

What is SPF?

SPF stands for Sun Protection Factor. Sunscreens are rated by the Sun Protection Factor (SPF) system which is mainly a measure of UVB protection.

The numeric value simply indicates how much longer that sunscreen can enable you to stay in the sun before you start experiencing sunburn. For example, the SPF 15 sunscreen allows a person to stay out in the sun 15 times longer. So, if you usually take 20 minutes to burn, the sunscreen will delay the onset of a sunburn to 300 minutes.