Exposure to large amounts of naphthalene may damage or destroy some of your red blood cells. This could cause you to have too few red blood cells until your body replaces the destroyed cells. People, particularly children, have developed this problem after eating naphthalene-containing mothballs or deodorant blocks. Some of the symptoms of this problem are fatigue, lack of appetite, restlessness, and pale skin. Exposure to large amounts of naphthalene may also cause nausea, vomiting, diarrhea, blood in the urine, and a yellow color to the skin.
Animals sometimes develop cloudiness in their eyes after swallowing naphthalene.
It is not clear if this also develops in people. When mice were repeatedly exposed to naphthalene vapors for 2 years, their noses and lungs became inflamed and irritated. No studies are available in people. Naphthalene has caused cancer in studies in female mice, but not in male mice or in rats of either sex. Tests are available that measure levels of naphthalene and its breakdown products in urine, stool, blood, or maternal milk.