Unless you've been living under a rock (and in that case you probably don't need to worry about sun damage), you know that too much sun exposure can cause skin cancer and premature aging. You know that it's important to wear sunscreen every day.

Beyond knowing you need to use sunscreen, you need to know which sunscreen ingredients offer the best protection, how much to use, and how often to apply it.

Protect Yourself from UVA and UVB Rays

UVB rays cause damage to the epidermis, the top layer of the skin, resulting in burning, and are a factor in premature aging and skin cancer. UVA rays penetrate deep into the skin and can cause everything from premature aging to skin cancer and immune-system damage. UVAs account for as much as 80% of skin damage from the sun. Therefore it is critical that you use a sunscreen that protects you from both UVA and UVB rays.

What is SPF in Sunscreen

The SPF (sun protection factor) of a sunscreen is a number that indicates how long you can stay in the sun without burning. For example, a sunscreen with an SPF of 15 means that if you normally start to burn in 20 minutes without sunscreen, if you wear SPF 15 you should be able to stay in the sun 15 x 20 minutes or 300 minutes. HOWEVER, many sunscreens wear off after swimming or excessive perspiration or they are unstable, like avobenzone, and wear off after exposure to sunlight. Therefore most sunscreens need to be reapplied frequently.

Best Sunscreen Ingredients for both UVA and UVB Protection

Unfortunately, the SPF measurement is only for UVB rays; there currently is no rating system for protection from UVA rays. The best way to make sure you are getting protection from both UVA and UVB rays is to use a sunscreen that provides "broad-spectrum UVA/UVB protection." Typically these products will contain avobenzone (also known as Parsol 1789), which blocks and absorbs UVA rays, and titanium dioxide, zinc oxide, or Octocrylene, which block and absorb UVA and UVB rays. Other common sunscreens are oxybenzone (UVA/UVB), and homosalate, octinoxate (methylhexyl methoxycinnamate), and octisalate which provide UVB protection.

Mexoryl SX - Strong UVA Protection Newly Approved by FDA

There is a new broad spectrum sunscreen that has received FDA approval called Mexoryl SX, also called ecamsule. It provides powerful protection against UVA and UVB rays. Dr. Stephen Stone, president of the Academy of Dermatology, told ABC News, "... It is an effective UVA blocker... it offers longer protection than other suncreen ingredients." Products that contain Mexoryl SX include La Roche Posay Anthelios SX Daily Moisturizer with SPF 15 3.4oz

How to Apply Sunscreen

You need to apply about a shotglass full of suncreen to your face and body in order to get enough protection. Since many sunscreens wear off due to sun exposure, swimming or perspiration, you should reapply it every hour or so. It is also important to apply the sunscreen 1/2 hour before you go out to give it enough time to absorb. Click here for our article on how to protect yourself from sun damage.