Drowsiness in infants after bumping their heads may be caused by concussion, brain contusion, brain hemorrhage, etc. Differential diagnosis by a doctor is required. 1. Concussion: If the concussion is caused by bumping the head, drowsiness and lethargy may appear. 2. Cerebral contusion: impaired consciousness is one of the most prominent symptoms, which is manifested as drowsiness, lethargy and blurred consciousness. 3. Cerebral hemorrhage: Cerebral hemorrhage can lead to increased intracranial pressure, which can make the brain function abnormal and can cause drowsiness, coma and other symptoms. It is recommended that parents take their children to regular hospitals in time to clarify the cause of the disease and carry out standardized treatment under the guidance of doctors, so as to avoid delaying the condition and bringing adverse effects to the baby’s body.