Sunscreen vs. Sunblock

Dr. Loretta's answer: There is currently no true distinction between the terms sunscreen and sunblock. Instead, when a formula does not have any chemical UV-absorbers, it is called “chemical free”. The distinction between sunscreen and sunblock is pretty much outdated in favor of the newer classification but about a decade ago, it was proposed that sunblock refer to physical UV agents and sunscreen refers to chemical UV absorbers, but this distinction has not gone into practice. Sun protection active ingredients can be classified into two major types: chemical and physical UV blockers. Chemical sunscreens contain special ingredients that act as filters to absorb UV and reduce ultraviolet radiation penetration to the skin. These sunscreens often are colorless and maintain a thin visible film on the skin. These sunscreens usually contain UVB and UVA- absorbing chemicals. The physical, sun-blocking ingredients are only two: titanium dioxide and zinc oxide which physically block ultraviolet radiation (UVR). A chemical free formulation will have one or both of these as the active ingredient(s).