Baldness in 4-year-old babies may be caused by immune dysfunction or genetic factors, and the cause should be clarified in a timely manner in the hospital. Patchy baldness is commonly known as “ghost shaved head”. Patchy baldness is a sudden localized patchy hair loss, hair loss area with clear boundaries and no scarring, when patchy baldness occurs, there is usually no special feeling, and the appearance of the scalp has no redness, swelling, flaking and other inflammatory reactions. 1. Immune dysfunction: The main task of the human immune system is to recognize and resist the attack of external microorganisms. However, in some cases, T-lymphocytes in the immune system, which are dysfunctional, cannot distinguish normal cells and attack hair follicles, generating specific immune responses and destroying the structure of normal hair follicles, leading to abnormal hair growth, reduction and patchy alopecia. 2. Genetic factors: Some studies show that 25% of patients with patchy baldness have a family history. Identical twins with identical genes are far more likely to suffer from baldness at the same time than dizygotic twins, which suggests that it is related to heredity. If your baby has symptoms of baldness, you should go to the hospital in time to avoid delaying the condition or causing adverse reactions.