While the clinician must first rule out obstructive causes of vomiting in infants, nonobstructive causes are more common than obstructive causes Nonobstructive causes of vomiting in this age group include GI, infectious, neurologic, renal, and metabolic disorders GER is a common cause of emesis in this age group GER results when relaxation of the LES allows retrograde passage of gastric contents Infants with GER may present with repeated episodes of emesis of stomach contents usually within 30 minutes of feeding Emesis is generally nonbloody and nonbilious, and is fairly constant over time Most infants will have some degree of GER or “spitting up,” with a peak at age months (up to 67% of infants) and gradually tapering over the first year of life GER that causes troublesome symptoms for the patient is referred to as gastroesophageal reflux disease (GERD) Troublesome symptoms that suggest GERD include poor weight gain, vomiting associated with irritability or refusal to feed, arching of the back during feeding, and respiratory symptoms such as cough or wheezing related to reflux For infants who present with reflux but without any of these troublesome symptoms, there is generally no need for any further diagnostic testing or for medical management Nonpharmacologic treatments suffice for the vast majority of infants with reflux Upper GI contrast radiography and esophageal pH probes are the most commonly used tests in the diagnosis and evaluation of GERD, but are almost never indicated in the PED for reflux evaluation Management of both GER and GERD should include lifestyle modifications These modifications can include feeding changes such as avoiding overfeeding, thickening feeds, and continuation of breastfeeding As milk–protein allergy can mimic GERD, a trial of eliminating milk and eggs from the diet of mothers of breast-fed infants or a trial of hydrolyzed protein formula in formula-fed infants may be warranted Medications should be reserved for infants with continued worrisome symptoms of GERD after trials of feeding modifications, with the two classes of medications most commonly used in infants being histamine-2 receptor antagonists (H2RAs) and proton pump inhibitors (PPIs) Medications should be given a 2- to 4-week trial, with weaning if symptoms improve It is important to stress to parents that these medications will reduce acid exposure in children with GERD, but that they will not decrease the amount of reflux itself There has been a shift away from acid-suppression therapy because of lack of efficacy and possible adverse effects Viral gastroenteritis is another common cause of vomiting in infants The infant will generally present with diarrhea as well, although they may present without diarrhea or early in the disease course before diarrhea has developed It is crucial