Thinning hair in infants may be caused by heredity, occipital baldness, malnutrition, hypothyroidism and other reasons. 1. Heredity: thinning hair in infants may be caused by genetic factors, the parents have less hair growth, the baby’s hair may also be thinner. 2. Pillow baldness: babies who lie on their backs for a long time, with their back pillows rubbing against each other, may have thinning hair. 3. Malnutrition: Infants due to insufficient breastfeeding or supplemental food added too late, too little, may cause its malnutrition, the body lacks vitamins and other nutrients, is not conducive to the growth of hair, will lead to thinning of baby hair. 4. Hypothyroidism: infants with hypothyroidism, metabolic dysfunction of the body, which can lead to insufficient supply of nutrients to the scalp, hair thinning, hair loss, there will be the performance of thinning hair. Thinning hair in infants may also have other causes, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.