What is the key difference between physical and chemical sunscreens?

The key difference between physical and chemical sunscreens lies in their mechanism of action concerning UV rays. Physical sunscreens, often containing active mineral ingredients such as zinc oxide or titanium dioxide, work by sitting on the surface of the skin and reflecting UV rays away from the skin. This means they provide a barrier that prevents the sun's harmful rays from penetrating the epidermis.

On the other hand, chemical sunscreens are designed to absorb UV radiation through their chemical formulation. These sunscreens usually contain organic (carbon-based) compounds that essentially convert UV rays into heat, which the skin then releases.

Understanding this fundamental distinction helps in selecting the appropriate type of sunscreen based on skin type, environmental conditions, and individual preferences. The other options provided do not accurately represent the primary functions or characteristics of physical versus chemical sunscreens. For instance, thickness and reapplication frequency can vary widely among different products and are not definitive traits that distinguish these two types of sunscreens. Similarly, not all chemical sunscreens are unsuitable for sensitive skin, as formulations can cater to various skin concerns.