Definition: Sunblock is different than sunscreen. A sunblock physically blocks the sun's UV radiation of the skin, both UVA and UVB. Examples of sunblocks are clothing, umbrellas, and trees. Chemical sunblocks scatter, reflect, and physically block UV radiation. The most well-known chemical sunblock is zinc oxide. Other commonly used sunblocks are talc, titanium dioxide, and red vetenary petrolatum.

Sunblocks do have some disadvantages. Many older chemical sunblocks are opaque, the skin can not be seen through the sunblock. This may not be cosmetically acceptable for many people. They can also be greasy and clog pores, a problem for people with acne-prone skin.

A new sunblock formulation has been developed that contains micronized titanium dioxide. The advantage of this formulation is that it is almost invisible and still has good UV blocking capabilities.