Most causes of vomiting in children are benign and self-limited. But vomiting can be a sign of a more serious condition. Persistent vomiting, for example, can lead to dehydration and electrolyte imbalances. When assessing whether the cause of vomiting is serious, doctors usually ask about the frequency of the vomiting, its color, whether there is blood or bile in it, and if the child has an underlying medical problem.
According to the Johns Hopkins Children’s Center, viral gastroenteritis is the most common cause of vomiting in children. Some viruses that cause gastroenteritis include rotavirus—the leading cause of gastroenteritis in children, and the Norwalk virus, which is responsible for epidemics of “stomach flu” on cruise ships. Bacterial causes of gastroenteritis include the microbes responsible for food poisoning, E. coli, Salmonella, and Shigella. All these microorganisms can cause vomiting and diarrhea, although the gastroenteritis caused by bacteria tends to cause blood in stools. Dehydration is the most common complication of vomiting due to gastroenteritis.
A common cause of vomiting in infants is gastroesophageal reflux disease, or GERD. In babies, the lower esophageal sphincter, a band of muscle that wraps around the lower part of the esophagus to prevent the backward flow of stomach contents, is weaker than in adults. This is thought to contribute to GERD in children. Children with GERD have frequent vomiting, particularly after eating, and spit up a lot. Parents of babies with GERD report their children vomit undigested food or curdled milk. Most children with GERD will eventually outgrow it. In the meantime, there are several things parents can do, from slowing down the feedings, to positioning the baby at a 45-degree angle during and after feeding. Some babies need medicines to decrease the amount of reflux. Occasionally, a child with severe reflux and vomiting may need surgery to eliminate the reflux.
Some children will vomit because they have an obstruction somewhere in their gastrointestinal tract. One-month-old infants can have pyloric stenosis, a tightening of the outflow section of the stomach that prevents milk from moving into the intestines and causes vomiting. Any child can have malrotation, an abnormal twisting of the gut within the abdomen. Children with malrotation usually vomit bile. Children who have had abdominal surgery in the past may have adhesions, or bands of tissue scarred over inside the abdominal wall at the point of the surgery, which can also cause vomiting. Intussusception, an intermittent telescoping of one part of the intestine unto another, is another cause. It is characterized by bouts of pain and vomiting.