A child with a fever of 39.9 degrees can be cooled down by physical methods and the use of medication. It is also important to treat the cause of the fever. 1. Physical methods: children with a fever of 39.9 degrees, parents can use a warm towel or fever stickers placed on the baby’s forehead, or use warm water to wipe the baby’s forehead, neck, armpits, thighs and other large blood vessels, in order to achieve the purpose of cooling. At the same time, give the baby more water. 2. drug cooling: in the use of physical cooling at the same time, parents can give the baby under the guidance of the doctor to use ibuprofen, acetaminophen and other drugs to lower the temperature. At the same time for the cause of the treatment for the temperature recovery is also very important, such as bacterial infections caused by respiratory tract infections, need to actively use antibacterial drugs such as cefaclor, cefdinir and other anti-infective treatment. A fever of 39.9 degrees is considered high. If your baby has a fever of 39.9 degrees for a period of time, it is recommended that you take your baby to the hospital for evaluation and treatment by a specialist to prevent delays. All the above medications should be used under doctor’s supervision, avoid self-medication.