The layering of toenails in a 3-year-old child may be caused by genetic factors, toenail trauma, lack of nutrients, tinea pedis and other reasons. 1. genetic factors: toenail two flaps for autosomal dominant inheritance, that is, flap nail, observe the toenail will have layered phenomenon. 2. Toenail trauma: 3-year-old children’s toenails kicked or hit hard objects, toenail damage will occur, the phenomenon of toenail layering. 3. Nutritional element deficiency: 3-year-old children are usually overly picky eaters, which may lead to the lack of nutrients in the body, such as zinc, iron, calcium and other nutrients are insufficient, which will lead to malnutrition of the toenail, the phenomenon of fracture and layering. 4. Tinea pedis: Tinea pedis occurs when the toenails of a three-year-old child are infected by fungus, which can cause localized damage to the toenails of children and the phenomenon of layering. 3-year-old children’s toenail layering causes more, specific to go to the hospital through the examination to determine.