According to the Centers for Disease Control, skin cancer has become the most prevalent form of cancer in the United States. To prevent against this threat, more and more people are turning to the regular use of sunscreen. The Sun protection industry has taken off; sunscreens are now found in makeup, clothing, lotions, even in lip balm. However, all sunscreens are not created equal.

Sunscreens work by absorbing, scattering, or reflecting sunlight off of the skin. Organic chemicals found in sunscreen, such as para aminobenzoic acid (PABA) and oxybenzone, absorb the Sun's ultraviolet rays before they have a chance to penetrate deeply into the skin. Other chemicals, namely zinc oxide or titanium oxide, are reflective particles that reflect incoming ultraviolet radiation away from the skin.

Unfortunately, although sunscreens provide a significant amount of protection from the sun, these chemicals are not 100% effective. Even after the application of sunscreen, all sun exposure carries with it some risk.

To minimize the risk from the sun's harmful rays, use of a "broad spectrum" sunscreen is recommended. Broad spectrum coverage refers to protection from both UVA and UVB rays – two different forms of ultraviolet radiation from the Sun. According to the Centers for Disease Control, UVA rays are the most common kind of sunlight at the earth's surface. UVA rays penetrate past the outer layer of skin and can lead to premature aging, damaged connective tissue, and an increased risk of developing skin cancer. Most UVB rays are absorbed in the atmosphere, but those that reach the surface of the earth contribute to the tanning and burning of skin. As such, UVB rays also contribute to a person's risk of developing skin cancer.

In addition to selecting a sunscreen that has broad spectrum coverage, a high Sun protection factor, or SPF, is recommended. SPF is a number which helps determine how long a person can spend in the Sun. According to Anne Marie Helmenstine, Ph.D., SPF only indicates protection from UVB rays, those rays responsible for the tanning and burning of the skin. It does not indicate protection from UVA rays, which can also lead to skin cancer and premature aging. A higher SPF indicates that more UVB rays are reflected or absorbed by the sunscreen, decreasing penetration of those rays into the skin.

SPF is simply a multiplication factor. If a person can spend 20 minutes in the Sun before getting burned, using a sunscreen of SPF 10 would allow that person to stay 200 minutes, or 10 times 20 minutes in the Sun before becoming burned. An SPF 15 sunscreen would allow that person to stay 300 minutes, or 15 times 20 minutes, out in the Sun before becoming burned.

This post was contributed via Seed.com, AOL's new platform for freelance writers.