Unprotected sun exposure is the most preventable risk factor for skin cancer, including melanoma.

Your best outdoor defense is sunscreen. When choosing a product, read the label and look beyond the SPF (Sun Protection Factor).

SPF only measures protection against UVB rays, the kind that are closer to the earth and make you feel hot.

Newer “broad spectrum” sunscreens also protect against UVA rays, those that are farther away, but penetrate more deeply into the skin. Sunscreen’s active ingredients work by absorbing, scattering or reflecting ultraviolet (UV) light.

Sunscreen should be applied at least twenty minutes before you go outside because it takes time for the compounds to start working, and it needs to be re-applied every two hours, as a guideline from the American Academy of Dermatology.

The Skin Cancer Foundation says that one blistering sunburn as a child more than doubles a person's chances of developing melanoma as an adult.

Sunscreen generally has a shelf life of three years or less, even if there’s not an expiration date on the bottle. And the active ingredients break down faster when sunscreen is left in the heat of a car or direct sunlight.