What is the Difference Between a Sunblock and a Sunscreen?

Sunblocks (physical sunscreens) are opaque formulations which absorb, reflect and scatter up to 99% of both UV and visible light. Because they are messy and may stain clothing, sunblocks are often used on such sun-sensitive areas as the nose, lips, ears and shoulders. Examples of ingredients in sunblocks are zinc oxide and titanium dioxide.

Sunscreens (chemical sunscreens) absorb specific wavelengths (range of 200-400 nm) and are classified as drugs by the FDA because they are ...intended to protect the structure and function of the human integument against actinic damage. Sunscreens are considered more cosmetically refined due to their pleasing consistency and are, therefore, typically used over a prolonged time for effective photoprotection.