Sunscreens reduce the amount of ultraviolet light that reaches your skin by absorbing, reflecting and scattering the light rays. Choosing a sunscreen requires your own judgment. People with darker skin have some natural protection but are not free of risk for skin cancer. There are PABA-free products that contain benzophenones and anthranilates that are irritating to fewer people. Sunscreen labels are not very specific about how often and how much of their product should be applied.
Recent studies indicate that most people use only about half of what is needed for full protection.
If you spend a lot of time in the sun, don't be tempted to make your sunscreen last longer by using less. It is recommended that you apply a sunscreen about 30 minutes before you go into the sun. This allows adequate absorption so that the sunscreen will be less likely to wash off by perspiration. The best way to avoid melanoma and other skin cancers is to cover exposed areas of skin with opaque clothing and wear a wide-brimmed hat to protect your head and face. Use a sunscreen when you will be exposed to the sun for a long period of time.