Nausea, the possible causes

Although it is an unpleasant sensation, it has an important function of defense against toxic substances and an alarm signal for many diseases. That’s why sometimes it comes to us

The feeling of having to empty the stomach typical of nausea can be debilitating but, in itself, it is not a disease. On the contrary, it has a very specific function: to protect against ingested toxic substances.

On balance, nausea is one of the most frequent disorders: one in two adults suffers from it at least once a year.

The causes of nausea can be very different from each other: from purely gastric problems, caused for example by a too heavy meal, to disorders that affect other organs, such as liver, pancreas, intestine, kidneys, gallbladder, heart, lungs.

But also some signals generated directly in the brain can cause this unpleasant sensation.

Finally, nausea can also occur during pregnancy.

A disorder with very specific characteristics

When nausea occurs, it is well recognizable from the first signs. An annoying, but not painful, sensation appears first, localized at the bottom of the throat, associated with increased salivation and disgust and repugnance towards food. It can be accompanied by the feeling of having to vomit, fatigue and exaggerated weakness and a sense of dizziness. Depending on the disorder that triggered the nausea, there may also be intense sweating, fever, pallor, tachycardia, increased blood pressure, bloating with meteorism, disorders similar to those of colitis with diarrhea and abdominal cramps.

A defense mechanism

The most frequent reason is irritation of the stomach. Typically, an unhealthy food has an unpleasant smell or taste. However, sometimes neither taste nor smell help to flush out dangerous foods and it can happen to ingest spoiled foods or to which you do not know you are allergic.

For this reason, the body has developed a defense system that, by emptying the stomach, avoids more serious consequences.

And, like toxins, bacteria and viruses can also stimulate nausea to eliminate the harmful agent. Viral or bacterial gastroenteritis has in fact among its most relevant symptoms nausea, along with diarrhea and abdominal pain. Let’s see which are the species that more than others can cause these disorders.

Bacteria Helicobacter


Escherichia coli


Virus Norovirus


Similarly, peptic ulcer, which damages the protective layer of the stomach, and reflux of gastric material into the esophagus may be associated with the feeling of having to vomit.

In addition, diabetes sufferers may develop a condition called gastroparesis that promotes nausea.

Last but not least, alcohol, smoking, some antibioticsnon-steroidal anti-inflammatory drugs (the so-called NSAIDs), chemotherapy and radiotherapy can irritate the gastric walls.

When the cause is the digestive system

Digestive disorders due to a meal consisting of overly processed foods are the most frequent cause of nausea.

Similarly, peptic ulcer, which damages the protective layer of the stomach, and reflux of gastric material into the esophagus may be associated with the feeling of having to vomit.

At the base of nausea there may also be other diseases affecting the gastric and intestinal systems, such as gastritis, intestinal obstruction or Crohn’s disease (or Crohn’s disease, as this disease is often mistakenly called).

Nausea can also be a sign of an attack of appendicitis or liver failure, or be one of the symptoms of renal colic (in which case it is associated with a sharp and sudden pain in the abdomen, at the height of the kidneys). It can also be one of the disorders of the so-called gastrointestinal influence. In this case there may also be episodes of diarrhea, abdominal pain, even high fever, headache and exhaustion.

In addition, those suffering from diabetes (but also other diseases, such as Parkinson’s, scleroderma, anorexia and bulimia, or have taken for a prolonged period some drugs such as opioids and some antidepressants) may develop a condition called gastroparesis, ie a chronic paralysis of a part of the stomach that causes a prolonged stay, at the gastric level, of ingested food, which promotes nausea.

Nausea can also be a sign not to be underestimated of the presence of an oncological disease and in particular of a tumor of the gastrointestinal area, such as pancreatic, stomach, colorectal and esophagus.

Last but not least, also alcohol, smoking, which can irritate the gastric walls.

Beware of medication

Nausea could be caused by drug therapy, especially if the disorder appeared on the same days as the treatment began, if it is constant and is not related to already known reasons.

In particular, some antibiotics and non-steroidal anti-inflammatory drugs (so-called NSAIDs) can irritate the gastric walls and cause nausea. The cause may not be the drug itself, but nausea may be caused by too high a dose or by a particular sensitivity of the individual to that active ingredient.

This disorder may also have metabolic reasons, due to drug interactions. In fact, it can happen that one medicine slows down the metabolism of the other, increasing its level in the blood.

Finally, nausea also associated with a sense of burning in the mouth and disgust and exaggerated fatigue, is often one of the side effects of cancer treatments such as chemotherapy and radiotherapy.

Messages coming from the brain

Stimuli that irritate the brain can also cause feelings of nausea and the desire to vomit. In fact, this organ needs very precise conditions in order to function properly.

Concentrations of sugars and fats must be appropriate and if they are not optimal, or the temperature or pressure are not adequate, the gag reflex can be triggered.

For this reason, trauma to the head, infections such as meningitis, tumors, vertigo problems or motor disorders, alcohol, carbon monoxide poisoning, heat stroke, dehydration and even fatigue can be the triggers of nausea.

In addition, some smells or even sounds can arouse vomiting. The mechanism that is activated is that mediated by the vagus nerve, one of the nerves that control the basal functions of the organism.

A similar situation can also be created during journeys by car, boat, bus or airplane, because the images observed while moving do not always correspond to those received by the balance structures that are inside the ear. In these cases we speak of car sickness, seasickness, plane sickness or, more generally, motion sickness. Children suffer from it above all, in whom the disorder tends to disappear as they approach adolescence. However, adults may also be affected. Each time a movement is made, the labyrinth “registers” the location of the body and transmits the information to a particular area of the brain. If, however, the movements are too abrupt, as in a road full of curves, or in a ship with rough seas or on an airplane during an air vacuum, too much information arrives at the same time and goes into “tilt”. This “hyperstimulation” causes the symptoms of motion sickness, first of all nausea. To counteract it may be useful to eat during the trip, in small quantities, dry foods such as crackers or breadsticks.

Nausea and pregnancy

It is well known that nausea often accompanies pregnancy, especially during the first few months. About 8 out of ten women suffer from pregnancy sickness, which is sometimes accompanied by acidity. The reason has never been fully clarified. However, it seems to depend on increased levels of human chorionic gonadotropin, a hormone that is produced by the placenta in the early stages of pregnancy, and estrogen. It has been shown, among other things, that the latter are particularly high in women suffering from hyperemesis, that is, a form of nausea associated with vomiting, so intense and persistent as to cause weight loss and dehydration. Other hormones also play a role in pregnancy nausea, especially progesterone, which can slow down digestive processes during pregnancy.

In the last stages of gestation, however, it is the uterus that, by compressing the stomach, can cause a form of esophageal reflux that leads to burning in the esophagus (up to the throat) and nausea.

Nausea in pregnancy could also represent a sort of defense mechanism.

According to some psychologists, in fact, nausea could be interpreted as signs of a difficulty in welcoming the embryo and the development of the placenta and could be the symptom of an emotional reaction, which, acting on the neurovegetative system, also influences digestion.

Not to be overlooked, then, the fact that gestation triggers an immune defense that alters the secretion of gastric juices and that hormonal changes make the muscles of the intestine and stomach less active, complicating digestion.

Joycelyn Elders is the author and creator of EmpowerEssence, a health and wellness blog. Elders is a respected public health advocate and pediatrician dedicated to promoting general health and well-being.

The blog covers a wide range of topics related to health and wellness, with articles organized into several categories.

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