The main components of physical sunscreen are titanium dioxide and zinc oxide. Titanium dioxide can completely block UVB, but can only block the shorter wavelengths of UVA, can not block long light waves. Zinc oxide is an important and widely used physical sunscreen agent, shielding ultraviolet radiation for the principle of absorption and scattering, almost all wavelengths of UVA and UVB can be blocked, and higher security, but the disadvantage is that the coating will be white, and more sticky.
The mechanism of chemical sunscreen is to form a UV phagocytic barrier on the surface of the skin with the help of other film-forming substances, which will be absorbed and neutralized to avoid shooting into the skin. Common chemical sunscreen ingredients are diphenyl ketone, ethylhexyl salicylate, humulanic acid ester, cinoxa ester, disodium phenyl dibenzimidazole tetraflavate, butylmethoxydibenzoylmethane, and ethylhexyl methoxycinnamate. The disadvantages of chemical sunscreens are poor photostability and the need for repeated reapplication under prolonged sun exposure.[5] And if you choose a chemical sunscreen, you will need to reapply it again and again. [5] And if you choose a sunscreen that contains lead and mercury ingredients, long-term use can cause skin dependence and breakage of skin cells and structures.