In 1832, British scientist Charles Darwin, who is famous for his evolutionary theory of biology, wrote a letter to his father after having been at sea for more than a month, saying: “The misery I endured from sea-sickness is far far beyond what I ever guessed at.” Much later in the letter, Darwin goes on to make the following pronouncement: “If it was not for sea-sickness, the whole world would be sailors.”

In these statements, Darwin, is, of course, referring to the all-consuming symptoms of nausea and vomiting associated with seasickness. In Darwin’s case, these symptoms were particularly severe and continued to plague him even on land. Modern medical detectives theorize that he may have had a rare genetic problem called mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke (MELAS) syndrome, which he would have inherited from his mother. One does not, however, need to have any experience with rare diseases to empathize with the misery he describes. Nausea and vomiting are the great equalizers of men, stripping all sufferers of energy, ambition, and desire. Virtually everyone has experienced both symptoms.

Why do we vomit? 

Like diarrhea, nausea and vomiting are probably evolutionarily developed, protective mechanisms designed to rid the body of toxins. Why these symptoms spill over into motion sickness and inner ear problems is a mystery, but the answer may have something to do with the fact that many toxins affect the inner ear. Some scientists speculate that over eons of evolutionary time the ear came to use the same warning symptoms experienced with seasickness to alert the body to other problems, such as trouble controlling balance. Nausea and vomiting are universal symptoms. The threshold for their appearance is highly variable. While triggers are usually physical, the symptoms can also come from the mind itself. Vomiting can be triggered by great distress, and in some people undergoing chemotherapy, antianxiety agents can diminish “anticipatory” nausea.

The scientific literature devoted to studying nausea and vomiting is full of words like “probably,” “possibly,” and “perhaps,” which reflects the lack of full understanding of the subjects. Nausea is a subjective sensation, a queasy feeling, which seems to come from the stomach but is felt primarily in the head—a feeling that vomiting may soon occur, though not necessarily. Nausea is often accompanied by the need to lie down or even to sleep, by an inability to concentrate, and by lack of interest in one’s surroundings. In people suffering from nausea, the muscular activity of the stomach and intestines is slower than normal. As nausea progresses toward vomiting, sweating and increased saliva production occurs, the skin pales, and the heart rate increases.

Vomiting is an action

Vomiting is an action and is much better understood than the sensation of nausea. It begins with a masterfully coordinated sequence of muscular actions that are carried out by the upper portion of the gastrointestinal tract, working in reverse to bring stomach contents back up the esophagus to the throat and mouth. When a person vomits, the muscles are all recruited to expel the mess with great force. Once vomiting occurs, nausea often subsides, at least temporarily.

Nausea is a sensation

Nausea has many different causes, including the presence of drugs and toxins, primary gastrointestinal problems, inner ear problems, hormonal and other metabolic problems, and brain problems. In most circumstances of nausea and vomiting, the symptoms are acute (appearing suddenly in a previously stable individual) and self-limited, meaning that they get better on their own within hours to days. The most common causes of short-lived symptoms are side effects of medications, surgery when anesthesia is used, viral or bacterial toxins, motion sickness, and migraine headaches. The most common causes of longer lasting episodes are the hormonal changes that take place during pregnancy, the side effects of chemotherapy and radiation treatments used to treat cancer, and episodes of inner ear problems that provoke a severe, spinning dizziness that is triggered when a person changes head position.

Searching for the cause of nausea: pay attention to other symptoms

Nausea and vomiting may also be symptoms of more serious illnesses, particularly when the cause is not easily identified or the symptoms do not resolve in the usual few days of discomfort that are experienced with a stomach flu. Often other, associated symptoms point to the source of trouble. Primary stomach disorders, like ulcers, can produce nausea, particularly after eating, and abdominal pains or blood in the stool lead to the correct diagnosis. Other abdominal problems, like bowel obstruction, gall bladder disease, and pancreatic cancer, can cause significant abdominal pain along with nausea and vomiting. Nausea caused by liver disease might be associated with increased abdominal size or yellowing of the whites of the eyes. Severe headaches and lethargy are symptoms of increased pressure in the brain, which can cause what is known as “projectile vomiting,” – sudden, unexpected, and very forceful expulsion of the stomach’s contents. Dizziness and double vision along with nausea may point to an impending stroke in the brainstem.

Treatment

The stomach and the brain work together in normal digestion, and when something goes awry, the neurotransmitters in the brain play a role in producing nausea. This brain-gut connection is at the heart of attempts to treat the symptoms of nausea with drugs, which fall into two categories. The first category consists of drugs that increase normal gut muscle action; drugs in the second category act by blocking neurotransmitters in the brain and the nerves leading to the gastrointestinal tract.

Drugs from both of these categories are used in postoperative care and in cancer chemotherapy and radiation treatment, and drugs from one or both of these categories are often tried in cases of persistent nausea, while an attempt is made to discover the underlying cause of the symptom. Drugs that block histamine receptors, such as over-the-counter remedies containing dimenhydrinate and prescription patches containing scopolamine, are most helpful in cases of motion sickness.

All of these drugs have side effects, the most common of which are drowsiness and mood disturbances. The most troublesome possible side effect is involuntary, small, twitchy movements. In self-limited cases of nausea and vomiting such as stomach flus, it is probably safest to retreat to bed and sleep, without using pharmacologic interventions other than over-the-counter nausea and vomiting remedies. When suffering from an acute case of nausea and vomiting, remaining hydrated is important, but the stomach is likely to revolt against more than a tablespoon or two of water at a time until the vomiting has stopped completely. Ginger may have some value in calming the stomach; ginger ale is a good first beverage in recovery. Unlike Charles Darwin, who had more complex, chronic and undiagnosed bouts of vomiting, you will most likely recover and forget how miserable you felt.