Feeling nauseated or even vomiting is usually common to individuals with varying health conditions.

Nausea is the sensation that the stomach or other digestive outlet wants to empty itself, while vomiting or throwing up, is the act of forcible emptying of the stomach.

Vomiting is a violent act in which the stomach has to overcome the pressures that are normally in place to keep food and secretions within the stomach. The stomach almost turns itself inside out — forcing itself into the lower portion of the esophagus (the tube that connects the mouth to the stomach) during a vomiting episode.

Nausea and vomiting are usually inter-linked symptoms of an underlying health condition or weakness. It is never a primary illness and to treat well these symptoms have to look for the causative agent.

There are numerous causes of nausea and vomiting. These symptoms can originate from the stomach as seen in gastritis cases or association with other remote illnesses from the stomach, medications or medical treatments as well as mechanical obstruction of the bowel.

There are also central causes that are signals from the brain that cause nausea and vomiting. Headache, especially migraine, is commonly associated with nausea and vomiting.

Head injury and any illness or injury that increases the pressure inside the skull can cause vomiting. This rise in intracranial pressure may be due to brain swelling from trauma as seen in people with concussion or head trauma, brain infections such as meningitis or encephalitis, tumor, abnormal electrolyte and water balance in the bloodstream.

People with inner ear complaints, such as motion sickness, labyrinthitis and benign postural vertigo can also develop persistent symptoms of nausea and vomiting.

Noxious stimulus for example certain smells or sounds can cause centrally mediated nausea and vomiting. Whether it is the pain of a broken bone or the emotional shock of observing an event may cause nausea and vomiting in a few individuals. Such vasovagal events can cause significant symptoms in a certain group of the population.

In a vasovagal episode, the vagus nerve that helps control of basic body functions like heart rate, breathing and blood pressure is overly stimulated by horrible events; cause the heart rate to slow and blood vessels to dilate. This decreases blood flow to the brain to inflict various symptoms as seen in some individuals who faint or suffer a syncope episode.

Some common nausea and vomiting complaints are associated with illness. People with diabetes may develop nausea because of gastro paresis, a condition in which the stomach fails to empty properly and is likely due to the generalized neuropathy (failure of the nerves in the body to send proper signals to and from the brain) that is a complication of the disease.

People with diabetes can also develop nausea and vomiting should their blood sugars become abnormally high or low (hyperglycemia, hypoglycemia) because the sugar and insulin balance is disturbed.

Many illnesses associated with the intra-abdominal organs have symptoms of nausea and vomiting. These include digestive organ diseases, for example, hepatitis, gallbladder disease, pancreatitis,  inflammatory bowel disease,  kidney diseases (for example, kidney stones, infection, kidney failure) and some forms of cancer.

Vomiting as an atypical symptom of another disease

Some illnesses will cause nausea and vomiting, even though there is no direct involvement of the stomach or gastrointestinal tract.

Heart attack victims may experience nausea and vomiting as an atypical presentation of angina, especially if the myocardial infarction affects the inferior or lower part of the heart.

Lung infections for example, pneumonia and bronchitis may also cause nausea and vomiting, especially if the area of lung involved is near the diaphragm, the muscle that separates the chest form the abdomen.

Sepsis is an overwhelming body infection that spreads through the bloodstream and is strongly associated with nausea and vomiting.

Eating disorders

Patients with bulimia will have self-induced vomiting, purging as part of their psychiatric illness.

Side effects from medications

The side effect of many medications include stomach irritation, nausea and vomiting. Anti-cancer dugs are notorious irritants for example, chemotherapy treatment.

Narcotic pain medications, anti-inflammatory medications, including both steroids like prednisone and non-steroidal medications like ibuprofen and antibiotics, all have nausea and vomiting listed as common side effects.

Cancer treatments such as chemotherapy and radiotherapy cause immediate and sometimes delayed symptoms of nausea and vomiting.

Pregnancy is another health condition with symptoms of nausea and vomiting especially common in the first trimester and is due to hormone level changes in the bloodstream.

Poor gastro-intestinal conditions such as abdominal pain and distention, nausea and vomiting or inability to pass out gas or flatus (gas) are usually hallmarks of poor intestinal health.

Due to a variety of potential reasons, the small intestine becomes blocked and does not allow contents to pass through the colon. This acts like a dam in which food, fluid, and secretions back up to cause obstructive related symptoms. In such circumstances, you feel as if the abdomen is going to burst due gas bloats or even fecal impaction in the large bowels. The later occurs to individuals with constipation.