Zinc oxide is an inorganic compound that is used in a wide variety of products, including cosmetics, medical formulations, ointments, ceramics, batteries, plastics, glass, rubber, paints, and even as a white pigment additive and food ingredient additive. Its more commonly known use, however, is as a UV blocker in sunscreens. The substance occurs naturally in the somewhat rare mineral zincite, but the majority of zinc oxide us commercially is synthetically produced.
Zinc oxide functions as a UV blocker by deflecting the sun’s rays on contact, preventing sun damage from occurring in the deeper layers of the skin.
While zinc oxide can be used on its own in sunscreen formulations, it best protects against UVA rays, the type of UV rays most commonly associated with sun spots and photoaging.
Because zinc oxide deflects UV rays — rather than absorbing them the way chemical sunscreen ingredients do — it’s known as a physical sunscreen ingredient. Since zinc oxide is not a broad spectrum ingredient (meaning it only blocks one type of UV ray, not both UVA and UVB rays), it’s not often used on its own to protect against sun damage. Instead, zinc oxide is incorporated in formulations with other UV blocking ingredients, whether chemical or physical.
Zinc oxide naturally has a white, powder-like consistently that is insoluble (meaning it cannot be dissolved by water) and is frequently used in everything from mineral cosmetics to diaper rash creams.