4 months baby fever 38.5 ℃ can be seen in respiratory infections, intracranial infections, Kawasaki disease and other conditions, whether it will affect the brain needs to be based on the cause and severity of the disease to determine, such as serious intracranial infections may affect the brain. 1. Respiratory tract infections: such as acute upper respiratory tract infections, clinical fever can occur, it is generally believed that the disease is caused by bacterial or viral infections, regular and reasonable treatment has a better prognosis, and generally will not affect the brain. 2. Intracranial infections: such as bacterial meningitis or viral encephalitis, may appear fever 38.5 ℃, severe cases may appear repeatedly high fever, temperature drop is not ideal, accompanied by convulsions, severe cases of the disease may affect the brain, epilepsy, motor and language development and other disorders. 3. Kawasaki disease: also known as cutaneous mucocutaneous lymph node syndrome, the above phenomenon can occur, accompanied by skin rashes, chapped lips and other symptoms, the disease does not usually affect the brain, can involve the heart, coronary artery dilatation, myocarditis and other conditions. There are many other causes of fever in 4-month-old babies, it is recommended to consult a doctor in a timely manner, whether the involvement of the brain needs to be combined with the baby’s condition by a specialist physician to make a judgment, and timely treatment, so as not to delay the condition.