Vomiting may lead to several complications, especially if it is recurring over a period of hours or days. Some of the complications associated with repeated vomiting include:

Aspiration of the vomitus into the air passage and lungs

More often than not, vomit contains gastric contents, which are acidic in nature. One of the common complications of vomiting is re-routing of the vomit to the air passages via the trachea and into the lungs. This is called aspiration.

Aspiration is not normally possible since the air passages are protected by the epiglottis which closes when fluid tries to enter. In addition, any tiny amounts of inhaled fluid usually leads to a cough reflex which expels the fluid effectively without causing damage to the lungs. However, the risk of aspirating the contents of the vomit becomes high when this protective cough reflex is weakened or abolished, such as when a person is heavily inebriated or sedated under general anesthesia. Unconscious people, babies and the very elderly also have poor cough reflexes, increasing their risk for aspiration.

Aspiration leads to choking, asphyxiation and aspiration pneumonia. Aspiration pneumonia is infection and inflammation of the lungs due to aspiration. It can be life threatening and may lead to respiratory failure if not detected and treated early.

Electrolyte and water loss

Excessive vomiting, especially over a prolonged period of time, leads to excess loss of water and electrolytes from the body. Electrolytes such as sodium, potassium, calcium, magnesium, bicarbonates and chloride ions are essential for normal bodily functions. As water is lost during vomiting, the delicate balance of electrolytes is also altered, which can lead to severe complications.

Expelling the gastric acid contents causes the loss of chloride and hydrogen ions which can lead to hypochloremic metabolic alkalosis, where there are high levels of bicarbonate and carbon dioxide but low levels of chloride, leading to an increased blood pH. In addition, there may be a low level of potassium (hypokalemia). Another problem is that vomiting makes it very difficult to both consume foods and fluids and to keep them down. This further aggravates the electrolyte depletion and deficiencies, worsening the condition.

Damage to the enamel of the teeth

This is commonly seen in people suffering from bulimia nervosa who purposefully induce vomiting on a regular basis as part of their illness. The acid content of the stomach that comes into contact with the enamel erodes and damages the teeth. The digestive enzymes in vomit also damage the gums which leads to dental complications.

Tear of the esophageal mucosa

This is termed Mallory-Weiss tear and occurs due to profuse vomiting that tears the inner mucosal walls of the esophagus. This manifests as reddish streaks of fresh blood in the vomit content.