According to a survey out of JAMA Dermatology, the information on sunscreen labels like meaning of SPF is not understood by many people. They also don't know how much product is needed to be used for protection.

There are many things about sunscreen one needs to know. SPF or sun protection factor measures ability of the sunscreen to filter U-VB rays. According to Dr. Jamie Davis, a dermatologist with Uptown Dermatology, it is a laboratory value, which measures protection by ultraviolet B light. One should know that SPF doesn't measure UV-A rays or tell anything regarding UV-A protection.

According to Davis, skin cancer is caused by both UV-A and UV-B lights. As per experts, UV-A penetrates deeper into the skin and could break down collagen and cause wrinkles. However, when it comes to UV-B rays, it's not the case. Davis said that A doesn't have a tendency to burn, whereas B could lead to this.

Dr. Davis said that some sunscreens offer protection against UV-B rays only, therefore, one should always go for the words 'broad spectrum' on the label. Such a product provides protection against both UV-A and UV-B. She also recommends that a sunscreen with zinc or titanium should be used since that physically blocks the rays, rather than chemically.

The SPF numbers indicates the time during which one can be in the sun before they burn. If one burns after one minute, wearing on SPF 15 will provide protection for 15 minutes and SPF 30 will protect for 30 minutes.