How thickly should I apply my sunscreen?
If you are wearing a bikini or swimming trunks, you will need to apply at least 1 ¼ ounces of sunscreen (a little more than a shot glass) to effectively protect all exposed skin. Spread on sunscreen at least ½ millimeter thick, and let it absorb into your skin at least 30 minutes before going outdoors. Remember to reapply every 2-3 hours.

Do I have to wear sunscreen on a cloudy day?
Even on a cloudy day, roughly 80% of the sun’s UV rays pass through the clouds. In addition to using sunscreen, it is highly recommended that you wear a hat, a light long-sleeved shirt to protect your arms, and sunglasses while outdoors. Also remember to apply sunscreen to your ears, neck and upper chest (décolleté). The latter are often-overlooked areas in terms of sun protection, but are equally susceptible to photoaging, as well as skin cancer.

Photoaging is a type of skin aging caused by a lifetime of sun exposure -- and that's not just the few days you spend at the beach every summer. Walking your dog, driving to work, and sitting in front of a sunny window are all examples of the type of sun exposure that you might not think of protecting yourself against. But over the years they can add up to wrinkling, pigmentation, and other signs of skin aging, as well as skin cancer.

Remember to choose a sunscreen that provides broad spectrum UVA and UVB protection, with a minimum SPF 15. Apply your sunscreen at least 30 minutes before going outdoors, and re-apply it every 2-3 hours, regardless of whether it is SPF 15 or SPF 50. Protecting your skin from the sun is one of the most important things you can do to keep your skin looking younger, longer.