About Sunscreen
There are two types of liquid sun protection, chemical and physical. Each works in a different way to protect your skin. Chemical lotions are known as sunscreens and traditionally use ingredients to absorb and disperse UVB rays, preventing them from penetrating skin. More recently, they also include ingredients to block UVA rays. Sunscreen can and should be used on a daily basis for regular activity like your work commute. Sunscreen is lightweight and transparent when it's applied.

About Sunblock
Physical lotions are known as sunblocks. These contain minerals like zinc oxide and titanium dioxide that physically create a barrier against both the sun's UVA and UVB rays. Sunblock is usually white, thicker and remains visible after you put it on. Sunblock is best used for anyone planning to spend hours in the sun at a time, say playing in a beach volleyball tourney. Most of us don't like the idea of being covered head to toe in what looks like white paint, and choose sunscreen, regardless. It's not pretty, but those are the facts.

Know Your SPF
What's with the SPF?: it's a number that theorizes how long you can stay in the sun when the product in question is applied, versus going out with bare skin. But it's tricky, and imperfect. Because age, sun strength, time of day and your genes all play a part in whether or not that number rings true for you. To make matters as simple as possible, just go with at least an SPF 30. According to studies, it blocks about 97% of the harsh rays that cause serious damage. It's said that SPF 45 blocks about 98%. What about SPF 75? According to the FDA, that's little more than marketing foolery, as no level of SPF protects 100% and the higher SPF numbers' increase in protection is negligible. Unfortunately, many people buy the highest SPF possible for themselves or their kids, thinking it means they can stay out all day long and be invincible to sun damage. They end up not re-applying and staying out longer than they would with a lower SPF that offers virtually the same protection.

Ingredients to Embrace, Ingredients to Stay Away From
Remember that you need protection against UVB and UVA rays. The physical nature of sunblock naturally protects against both, but not so with sunscreen. As of right now, SPF only indicates UVB protection. There's no rating system for UVA. Again, keep your eyes peeled for "broad spectrum," indicating that a sunscreen protects from both. Ingredients in sunscreen that protect from UVB are glycerol PABA, padimate A and padimate O. UVA protectors are oxybensone, sulisobenzone and Parsol 1789. Note: Some have an allergic reaction to PABA and therefore may look for sunscreens without it, which is also labeled.

Know How Much and How Often to Re-Apply
Even the most perfect SPFor the best sunblock does not protect against the sun for more than an hour or two. And that includes waterproof and water-resistant varieties. Always re-apply about every hour or so when you're outdoors. What about your moisturizer that has SPF 15? Unfortunately, that too will wear off after a couple of hours. Still, it's better than nothing on a day to day basis. Experts say that we should apply the same amount of lotion that would fit in a shot glass to protect our entire bodies, and that most people don't use enough. So don't be afraid to slather it on before you head out in your swimsuit.