The normal underarm temperature range for a four year old baby is usually between 36-37°C. If your child’s temperature is between 37.1-37.3℃, it is generally considered to be a transient increase in body temperature due to high room temperature or overdressing your child. It is recommended to dress the child appropriately and the temperature will drop when the child is quiet. However, if the baby’s temperature is between 37.5-38.1℃, it is considered that there is hypothermia. You need to give your child physical cooling, drink plenty of warm water to help your child dissipate heat. If your child’s temperature continues to rise above 38.5℃, you usually need to take safe and effective antipyretic medications for infants and children such as Merrill Lynch and Tylenol to help your child get rid of the fever as soon as possible. If your baby has a persistent reactive fever, it is recommended to take your child to the doctor as soon as possible for examination and then treat the symptoms.