As per your history is concerned Drooling of a child aged 4 month old can be due to a number of pathological causes so check his body temperature every 6 hours and record it to ruled out any infection present or not.Next check his respiratory rate or breathing rate per minutes and record it. Do Modifying feedings As a first step, it is recommend thickening feedings, which can be done by adding 1/2 to 1 tbsp rice cereal/30 mL formula. Thickened formula seems to reflux less, particularly when the infant is kept in an upright position for 20 to 30 min after feeding. Thickened formula may not flow through the nipple properly, so the nipple orifice may need to be cross-cut to allow adequate flow. Providing smaller, more frequent feedings helps keep the pressure in the stomach down and minimizes the amount of reflux. However, it is important to maintain an appropriate total amount of formula/24-h period to ensure adequate growth. In addition, burping the infant after every 1 to 2 oz can help decrease gastric pressure by expelling the air the infant is swallowing. A hypoallergenic formula can be given to infants who may have a food allergy. Hypoallergenic formula can even be helpful for infants who do not have a food allergy by improving gastric emptying. All children should be kept away from caffeine and tobacco smoke. Positioning After feeding, infants are kept in an upright, nonseated position for 20 to 30 min (sitting, as in an infant seat, increases gastric pressure and is not helpful). For sleeping, the head of the crib can be raised about 15 cm (6 in); if the head of the crib is raised, infants should be secured in a sling fitted over the mattress or wedge to keep them from rolling or sliding down to a horizontal position on the lower end of the crib. Drug treatment Three classes of drugs can be used in infants who do not respond to feeding modification and positioning: Histamine-2 (H2) blockers Proton pump inhibitors (PPI) Promotility drugs Typically, treatment is begun with an H2 blocker such as ranitidine 2 mg/kg po bid to tid. If the infant responds, the drug is continued for several months and then tapered and stopped (if possible). If infants fail to respond to H2 blockers, a PPI such as lansoprazole can be considered, although there are few data on PPI use in infants. PPIs are more effective at suppressing gastric acid than are H2 blockers and are given only once/day. For infants with GERD and an acute symptom such as irritability, a liquid antacid can be used. Infants who have gastroparesis may benefit from a promotility drug in addition to acid-suppressive therapy. Erythromycin is one of the most commonly used promotility drugs for this situation. Metoclopromide was used previously but does not seem as effective and can have significant adverse effects. More recently, amoxicillin/clavulanate has also been used for its promotility properties.(Thanks)