The ideal sunscreen agent would be chemically inert, safe and absorb or reflect through the full UV spectrum. Titanium dioxide meets these criteria limited only by aesthetics. By decreasing the particle size of this pigment to a micro-size or ultra-fine grade making it less visible on the skin surface, some of these advantages could be utilized. However it does not appear to stay on the surface as well as zinc oxide. Dermal adsorption is another problem because open skin can produce systemic levels. In children, where the body surface area is so great compared to the body weight, it is possible to get good adsorption. No toxicity results when the ingredient is placed on intact skin of older children or adults.
Titanium Dioxide is polymorphous. That is, it exists in three modifications or crystal structures, rutile, anatase or brookite. Only the anatase and rutile modifications are of any note, technically or commercially, and they are shown below.
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