The three most common causes of vomiting mucus are colds, allergies, and acid reflux. In respiratory situations, the mucus is usually dripping down from the sinuses and nasal passageways into the throat. When there’s enough of it, this can cause gagging and ultimately vomiting. Children tend to be some of the most vulnerable to mucus-filled vomit in these cases since their gag reflexes often aren’t as developed as adults’ are. In the case of acid reflux, the mucus is usually flowing up from the stomach and digestive tract. While it can certainly be unsettling for people to see mucus in their vomit, it isn’t usually a cause for concern, and many experts actually say that it’s pretty common. In most cases it will go away on its own as soon as the root cause disappears.
Mucus is a fluid that is secreted by the body’s mucus membranes. It is a thick, gum-like substance that occurs normally in places like the respiratory and digestive tracts — places that depend on the constant movement of different particles. It coats the walls of the nasal passages to collect outside elements like dust or pollen that might irritate someone and cause him or her to sneeze, for example, and it lubricates the air passages, making it easier to breathe. In the esophagus and stomach it acts as a coating to protect these organs from stomach acid that is released as a normal part of digestion.
A healthy human body produces anywhere from a quart to a gallon (0.94 to 3.78 liters) of mucus a day. When illness strikes, though, production often goes significantly up, and this is when vomiting becomes more likely. Irritation often triggers an immune response in the body, prompting more mucus to help either flood out the bacteria or virus or block the way for its spread. Excesses that flow into the throat or esophagus often cause vomiting not as a result of any sort of independent stomach problem, but rather as a consequence of overload.
People often produce the most mucus when they’re suffering from a cold, an upper respiratory infection, an allergy attack, or a coughing fit. In these instances, the mucus leaks from the sinuses and runs down the back of the throat — called “post-nasal drip” in medical circles — or is coughed up from the lungs; it may then be swallowed and end up in the stomach. When a person swallows too much of this secretion, it can cause vomiting as the body’s way of getting rid of it. Too much mucus or mucus that is very thick often causes nausea, too, and one of the body's natural responses is to trigger vomiting to ease that nausea.
Implications for Children
One of the biggest reasons young children sometimes fall prone to vomiting mucus is because of their generally sensitive gag reflex. A child with a cold, allergies, or a lung infection will typically secrete a great deal of mucus. That child may cough so forcefully trying to clear his or her airway that he or she triggers the gag reflex, and vomiting is often the inevitable result. In addition, children tend to swallow mucus rather than spitting it out or "coughing it clear" as adults do. This may occur when children have a severe infection, such as a sinus infection that creates thick, excessive secretions of mucus, or when they are too young to understand what’s happening.
Another cause of vomiting mucus may be due to acid reflux, which is also frequently called “heartburn” because of the burning, tight sensation it tends to cause in the upper chest. In people who suffer from heartburn, the stomach acid backs up into the esophagus. In order to protect itself, the body produces more mucus secretions. This excessive secretion is often swallowed back down into the stomach, and when there is too much, a person might feel ill and vomit up the excess.
Treatment and Prevention
There isn’t usually a cure for mucus vomiting and the condition will generally go away on its own as soon as the underlying cause — allergies, for instance, or a cough — disappears. People who have excessive mucus or find that they are constantly swallowing it or vomiting it back up may want to get the advice of a qualified healthcare provider, though. Certain medications can help keep mucus levels in check, which can reduce the risk of nausea and vomiting. Certain antacids can also help keep heartburn under control. Regularly clearing the nasal passageways and spitting rather than swallowing mucus that drips into the mouth can help, as well.
Constant mucus secretions and vomiting that seems to happen outside of some other identifiable condition may indicate some more serious condition, and should usually be evaluated. Infants and young children should also usually be treated for persistent mucus secretions to avoid the risk of choking, particularly during the night.