Which Chemicals Are in Sunscreen?

Sunscreens have evolved over the past few decades to offer a range of formulas to offer sun protection. The best sunscreens are called broad-spectrum sunscreens, because they can block light at a range of wavelengths to protect your skin from harmful UVA and UVB rays. A number of sunscreen ingredients have distinct UV-protection spectrums and mechanisms of action.

PABA

PABA, which stands for para-aminobenzoic acid, was the active ingredient in some of the first sunscreens developed. PABA works by absorbing UV rays from the sun and undergoing a chemical modification that changes UV rays into heat. Because the PABA in sunscreen absorbs UV rays, the underlying skin is protected. The National Skin Centre states that many modern sunscreens are formulated to be PABA-free, because it stains clothing, causes allergic reactions in a portion of the population and only protects against UVB rays.

Modern Physical Sunscreens

Physical sunscreens literally block your skin from the sun’s rays. They form a barrier that reflects UVA and UVB rays, so your skin is never exposed. Popular physical sunscreen ingredients are zinc oxide and titanium dioxide. When applied to the skin, both of these compounds form a white residue over the skin that acts as the barrier; however, the zinc oxide and titanium dioxide minerals are ground so finely in some formulas that the white residue is much less visible.

Physical sunscreens provide broad-spectrum protection against both UVA and UVB rays and continue to protect the skin from the sun until they are washed off.

Modern Chemical Sunscreens

Modern chemical sunscreens absorb UV rays and convert them to nonharmful forms of energy. Often, chemical sunscreen formulas will contain a few active ingredients to provide protection against both UVA and UVB rays.

Chemicals like cinnamates and octocrylene protect against UVB rays, while avobenzone and oxybenzone protect against UVA rays. You must reapply chemical sunscreens throughout the day, even if the sunscreen is not washed off. This is because the sunscreen becomes less effective over time due to the active ingredients being used up. To maintain the same sun protection level, they must be replenished.