Increased salivation, often called “watery mouth” or hypersalivation, before vomiting is a common physiological response. This involuntary response prepares the body for the expulsion of stomach contents. It protects against potential harm from highly acidic gastric fluid.
The Body’s Anticipatory Response
When the body anticipates vomiting, the nervous system initiates a complex reflex. Nausea signals, from sources like toxins, motion, or intense pain, begin this process. These signals converge on the medulla oblongata in the brainstem, which houses the vomiting center.
The medulla oblongata coordinates the vomiting reflex. This coordination involves the autonomic nervous system’s parasympathetic branch. The parasympathetic nervous system, responsible for “rest and digest” functions, stimulates salivary glands. Upon receiving signals from the vomiting center, parasympathetic nerves stimulate salivary glands, significantly increasing saliva production. This rapid, anticipatory salivation prepares the mouth and throat.
The Protective Role of Increased Saliva
The surge in saliva before vomiting protects the delicate tissues of the esophagus, mouth, and teeth from corrosive stomach acid. Stomach acid is highly acidic and can damage these areas, which lack the stomach’s protective mucus lining.
Saliva is slightly alkaline (pH typically just above 7), containing bicarbonate, calcium, and phosphate ions. This alkalinity helps neutralize stomach acid during vomiting. Increased saliva also dilutes acidic vomit, further reducing its corrosive potential. Additionally, this influx creates a protective coating on teeth, shielding them from acid erosion, and lubricates the pathway for easier expulsion. Studies show a higher rate of salivary bicarbonate secretion when esophageal mucosa is exposed to acid, highlighting its protective role.
Common Triggers for the Vomiting Reflex
The vomiting reflex can be activated by various stimuli, signaling the brain to expel harmful substances or indicating an internal imbalance. A common trigger is the presence of toxins in the gastrointestinal tract, such as those from food poisoning or certain medications. These toxins can directly stimulate receptors in the gut or activate the chemoreceptor trigger zone (CTZ) in the brain, an area outside the blood-brain barrier that detects circulating harmful substances.
Motion sickness is another frequent cause, stemming from disruptions in the inner ear’s balance system, which sends signals to the vomiting center. Strong odors or tastes can also induce nausea and subsequent vomiting, as can intense pain, emotional stress, or even anxiety. Conditions like migraines, pregnancy (morning sickness), and various infections, such as viral gastroenteritis, are also well-known triggers for activating this protective reflex.
When to Seek Medical Advice
While occasional vomiting and pre-vomiting salivation are typically not serious, certain signs warrant medical attention. It is advisable to consult a doctor if vomiting persists for more than a day or two in adults, or for shorter periods in children, or if it is so severe that fluids cannot be kept down.
Symptoms of dehydration, such as reduced urination, dry mouth, or confusion, are also indicators for seeking medical help. Immediate medical attention is necessary if vomiting is accompanied by severe abdominal pain, chest pain, a stiff neck and high temperature, or a sudden, severe headache. The presence of blood in the vomit, which might appear bright red or like coffee grounds, or green/yellow-green vomit, also requires urgent medical evaluation.