By swallowing too much fluoride for the child's size and weight during the years of tooth development, a child can develop enamel fluorosis. This can happen in several different ways. First, a child may take more of a fluoride supplement than the amount prescribed.Second, the child may take a fluoride supplement when there is already an optimal amount of fluoride in the drinking water.Third, some children simply like the taste of fluoridated toothpaste. They may use too much toothpaste, and then swallow it instead of spitting it out.