In most newborns the lower esophageal sphincter is relatively lax. Thus, frequent spitting up is common in infants. This is called physiologic reflux. These are normal, happy babies who eat well, gain weight, and who have no other symptoms. Still, this spitting up is often upsetting to parents. Physiologic reflux can also be quite inconvenient in that parents frequently must change clothes -- theirs and the child's. Over time, the lower esophageal sphincter becomes more competent; children eat more solid food; they assume a more upright posture. The spitting up diminishes. In most cases, the spitting up resolves without treatment by about 18 months of age. When reflux lasts beyond about 18 months, or when it is associated with other symptoms at any age, it should be evaluated. These other symptoms might include poor weight gain, heartburn, irritability (especially after eating or while lying down), bad breath, excessive cavities, wheezing, chronic cough, pain with eating, or recurrent pneumonias.