There are two kinds of UV rays from the sun that you need protection from: UVA and UVB. UVB light can damage the DNA in the outer layer of our skin, called the epidermis, as well as cause sunburn. UVA rays can shoot through to the middle skin layers, called the dermis. They can cause minor damage, such as tanning and wrinkles, as well as trigger DNA damage that can lead to skin cancer. For the average adult, the US Food and Drug Administration recommends using at least a shot glass–sized amount on your body every 2 hours, even on cloudy days. In addition to blocking all the kinds of sunlight that can damage skin, sunscreen needs to be spreadable and protect us. Different types of sunscreens achieve these goals in several ways. Take a look below at what the ingredients in a sunscreen  do.

ACTIVE INGREDIENTS: 10–30%

Probably the most important parts of sunscreen are the compounds listed as active ingredients. These sun filters, or ultraviolet filters, protect our skin from the sun.

The active ingredients in sunscreens protect our skin by either absorbing or reflecting UV light. Currently, 16 sun-filtering ingredients are approved by the FDA. Sunscreen in the US only uses 8 regularly: avobenzone, homosalate, octinoxate, octisalate, octocrylene, oxybenzone, titanium dioxide, and zinc oxide.

Other SUNSCREEN INGREDIENTS

FORMULATION STABILIZERS: 50–60%

Other ingredients in sunscreens don’t block the sun’s light, but help the active ingredients stay in the solution and not go bad. Preservatives, such as phenoxyethanol and tocopherol acetate, keep the active ingredients from breaking down or the formulation from having a shorter shelf life.

SENSORY ENHANCERS: 13–33%

Some ingredients in sunscreen change the way the product feels or smells. These compounds are what make people want to wear sunscreen, or help make people less averse to wearing it. Moisturizing ingredients, fragrances, and emollients can affect the way that it feels on the skin. Companies can technically sell sunscreens that contain only the sun filters, but such products would be grainy or greasy and difficult to spread.

For more information on what's in your sunscreen click here.