The three main areas of the body to detect temperature are the mouth, the anorectal mucosa and the axilla. The most commonly used clinical site for testing is the axilla. The axillary temperature is generally 36-37 ℃, plus or minus 0.1 ℃, for the normal body temperature range standard. 4 months baby temperature is 37.5 ℃, belongs to the fever in the low fever. For the time being, you do not need to give your baby medication, you can give your baby more warm boiled water, pay attention to warmth, still continue to breastfeeding, always test the temperature and blood routine, to clarify the cause of the disease, symptomatic treatment.