Dr Mercola Asks: Why Do We Vomit?

Dr. Mercola

Vomiting is a natural reflex that often occurs as a form of protection. In the event you consume something that is contaminated or poisonous, vomiting is your body’s way of getting rid of it. You may first experience nausea, which is the unpleasant feeling of being about to vomit.

Vomiting refers to the typically involuntary emptying of your stomach contents through your mouth. Nausea and vomiting are not diseases but rather are symptoms of an underlying health condition.

Often, a virus, such as norovirus, is to blame, but vomiting may also be due to bacteria, parasites and food poisoning. Other conditions, including motion sickness, pregnancy, reflux and even stress, can also cause vomiting.

How Vomiting Occurs

At the foundational level, the vomiting reflex is controlled by your brain’s vomiting center, the chemoreceptor trigger zone (CTZ), also called the area postrema. The CTZ is outside the blood-brain barrier, which means substances in your bloodstream have direct access.

This is why certain medications can trigger or stop vomiting. Various areas of your body can stimulate the CTZ and cause vomiting. This includes:1

• The vestibular system of your inner ear, which may trigger vomiting induced by motion sickness.

• The vagus nerve, the tenth cranial nerve that runs from your brain stem down to your abdomen. This may trigger vomiting induced by gastroenteritis (stomach flu) or when the back of your throat is irritated (gag reflex).

• Dopamine receptors, which may be activated by stress and lead to vomiting

The Three Phases of Vomiting

The vomiting process involves more than simply “throwing up.” It typically consists of three phases, as reported in The Clinical Journal:2

1. Nausea, sweating and salivation. Your parasympathetic nervous system causes excessive salivation to protect your tooth enamel from the acidic contents of your stomach. Your sympathetic nervous system leads to sweating and increased heart rate.

2. Retching

3. Expulsion of gastric contents through your mouth, which occurs, step-by-step, as follows, according to The Clinical Journal:3

” … inspiration [inhalation] lowers the thoracic pressure while the lower esophageal sphincter is contracted and the abdominal muscles are contracting forcefully, thus building up pressure within the abdominal cavity.

The intestines are undergoing negative peristalsis and as soon as their contents reach the lower esophageal sphincter, it opens and pressure is suddenly released, propelling the gastric contents out of the mouth through the relaxed esophagus.”

What Are the Top Causes of Vomiting?

In most cases, vomiting is caused by underlying conditions that will clear up on their own within a couple of days. Although it can be incredibly uncomfortable, such vomiting is not serious (as long as you don’t become dehydrated). Top causes include:4

Gastroenteritis (also known as stomach flu)

Noroviruses are the leading cause of gastroenteritis in the U.S., responsible for up to 21 million illnesses, 71,000 hospitalizations and 800 deaths each year.5

They generally cause a nasty infection that leads to diarrhea, abdominal pain and vomiting within 24 to 48 hours of exposure. Norovirus infection is often referred to as the “stomach flu,” although it shouldn’t be confused with influenza, which is a respiratory infection.

The symptoms of norovirus infection can be quite debilitating, but most people recover on their own within a few days. Those most at risk of complications (typically dehydration) are infants, the elderly and those with compromised immune systems.

The elderly living in nursing homes and children in day care facilities are often among those hardest hit, due to their close proximity with others and the highly contagious nature of these viruses. This is also the reason why cruise ships are sometimes associated with norovirus outbreaks.

To get an idea of just how contagious this group of viruses is, a person with norovirus infection may shed billionsof norovirus particles, but it takes just 18 of these particles to infect someone else.6

Food Poisoning

Many food-borne pathogens can lead to vomiting. As far as food poisonings go, noroviruses are strongly associated with restaurant-prepared or store-bought “complex foods” — foods that contain a number of ingredients so that the specific culprit cannot be pinpointed.

Ready-to-eat foods, including salads, sandwiches, ice, cookies and fruit, are also risks, although eating any food that is contaminated with vomit or feces from an infected person could lead to infection.7

So if a food handler is not careful, he could continue to spread vomit-inducing viruses to others for some time.

Even heating a food may not be enough to get rid of some pathogens; noroviruses, for instance, can survive heating up to 140 degrees F as well as quick-steaming methods often used to prepare shellfish.8 It can also survive being frozen.

Motion Sickness

Anytime your body moves in a way that’s different from what your eyes see, motion sickness can develop. Your inner ear, or vestibular system, is involved in movement and balance. This system senses motion, such as when you’re in a car or on a ship, and expects your eyes to confirm it.

When a mismatch or “sensory conflict” occurs, such as when you can feel the rolling of a ship but your eyes suggest you’re sitting still inside a cabin, nausea, vomiting and dizziness — the hallmarks of motion sickness — can occur.

The genomics company 23andMe found 35 genetic factors tied to motion sickness as well, including several that may be linked to nausea (other research suggests the nausea and vomiting associated with motion sickness may be activated by neural pathways).9

If you know you’re prone to motion sickness, focus your eyes on the horizon or another fixed point. If you’re in a car, be the driver or pretend you’re the driver.

Ear Infections

Ear infections may involve fluid buildup inside the ear, which can throw off your vestibular system and lead to nausea and vomiting, much like motion sickness.


Nausea and vomiting are very common in the first trimester of pregnancy. This is often referred to as “morning sickness,” although it can occur at any time of day.

Acid Reflux

Gastroesophageal reflux disease (GERD) is characterized by a burning sensation originating behind your breastbone, sometimes traveling up into your throat. In some cases, this burning pain can be severe enough to be mistaken for a heart attack.

You may also experience a sour taste in your mouth, frequent burping and even nausea and vomiting.

The answer to acid reflux is to restore your natural gastric balance and function. Eat lots of vegetables and other high-quality, ideally organic, unprocessed whole foods, and make sure you’re getting enough beneficial bacteria from your diet by regularly consuming fermented foods.


A stressful event can make you literally sick to your stomach, to the point that you vomit.

Vomiting: When to Worry

As mentioned, in most cases vomiting are the result of a stomach bug that will get better on its own in a couple of days. It may also be due to another self-limiting factor, like a long car ride or an upcoming exam that has you extremely stressed. That being said, the following signs and symptoms warrant medical attention above-and-beyond typical vomiting:10

Strange-colored vomit: Bright green vomit can be caused by bile, which could signal a blockage in your digestive system. Red or dark-colored vomit may be due to blood caused by an ulcer or other condition.

Projectile vomiting in infants: If your infant vomits forcefully, it may be due to a stomach blockage called pyloric stenosis.

Stomach pain: Intense abdominal pain along with vomiting and fever (but not diarrhea) may be a sign of appendicitis. Get to the emergency room immediately if you have these symptoms.

Vomiting after injury (such as a blow to your head or abdomen): This may be a sign of concussion or internal injury.

Vomiting soon after waking: This can be a sign of brain tumor, especially when accompanied by headache.

What to Do if You’re Vomiting Due to a Virus

Most people will be infected with a vomit-inducing virus such as norovirus at some point during their lives. If this happens, make sure the vomiting (and diarrhea) does not cause you to become dehydrated, as dehydration can be life threatening. If you begin to become dehydrated, it is vital that you go to an emergency room for evaluation and treatment.

Initially, however, if you have thrown up put your stomach at complete rest for at least three hours. Avoid water, crackers, soda — everything for the first three hours. Once three hours have passed and no further vomiting has occurred then try sipping small amounts of water slowly. If that is tolerated and you have not vomited further, you can gradually increase the water.

Do this for one to two hours and if that is tolerated then you are ready for the final phase — large doses of a high-quality probiotic, taken every 30 to 60 minutes until your symptoms go away.

Try Ginger at the First Sign of Nausea

One of the bestnatural remedies for nausea (and motion sickness) is ginger. At the first hint of nausea, consuming ginger may help the feeling go away, possibly even helping to prevent vomiting. To make ginger tea, slice off a small amount of fresh ginger and steep it in hot water for 30 seconds to several minutes. Ginger is very potent, so taste it at regular intervals of about 30 seconds — it can get very strong fast.

Alternatively, for a quicker solution, just take one-half teaspoon of finely diced fresh ginger and swallow it. Personally, this has worked for me every time I have had the need for it.


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