A white cast in sunscreen is the leftover white or grey tint of sunscreen on the skin, caused by the ingredients in physical sunscreen, such as zinc oxide and titanium dioxide. Mineral sunscreens use these minerals to diffuse the suns rays, instead of converting them to heat like chemical sunscreens. The white cast tends to come from particles of these minerals that either clump up or from particles that havent been absorbed fully into the skin for a variety of reasons. The white cast isnt harmful, and the chemicals that cause it (zinc oxide and titanium oxide) are among the healthiest sunscreen ingredients. In fact, the white cast can be a good thing because it helps you see where you have already applied sunscreen. However, some people may not like the appearance of the white cast, and there are ways to avoid it. For example, tinted sunscreen can solve the issue of a white cast, but it should be used carefully to match your skin color. Additionally, effective skincare tips can help avoid sunscreen white cast, such as rubbing the sunscreen in thoroughly and not applying too much sunscreen at once. Some sunscreens are formulated to avoid the white cast issue, such as Neutrogena Purescreen+ Mineral UV Tint Face Liquid Sunscreen, which has added tint to counteract the cast and create a mineral sunscreen that appears invisible.