Hair loss in three-year-old babies may be related to causes such as baldness and ringworm. 1. Patchy baldness: Patchy baldness is caused by a combination of genetic and environmental factors, genetic susceptibility is an important factor in the onset of the disease, about 25% of patients have a family history, in addition, neuropsychiatric factors are considered to be an important triggering factor. The phenomenon of patchy hair loss can occur. 2. Tinea capitis: Tinea capitis is a superficial fungal disease that occurs on the scalp, mainly affecting children, and is highly contagious. It can be caused by fungal infections such as rust-colored microsporidium, purple trichophyton, and hair-breaking trichophyton, which can lead to hair loss, hair breakage, and scaling. Parents are advised to take their children to the hospital in time to clarify the cause of the disease and standardize the treatment under the guidance of the doctor, so as not to delay the condition.