From Rod Brouhard,
Your Guide to First Aid.
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Nausea, with or without vomiting, is a miserable feeling. Most of the time, nausea is not life-threatening. However, prolonged nausea that causes repeated vomiting may lead to dehydration or even shock.

Causes of Nausea

There are several common causes of nausea and vomiting. Most causes of nausea either involve the gastrointestinal tract or are triggered by feelings of dizziness (vertigo). It's important to identify what is causing nausea in order to relieve it.

Some common causes of nausea:

• pregnancy
• infections
• food poisoning (foodborne illness)
• anxiety or stress
• alcohol intoxication
• fatigue
• brain injury
• vertigo
• motion sickness
• carbon monoxide poisoning
• reactions to medication

Infections that cause nausea usually affect the gastrointestinal system, but infections that lead to shortness of breath can cause nausea by depriving the brain of oxygen. Whenever the brain is affected by an illness or injury, there is always the possibility of it causing nausea. Vertigo, anxiety, stress, and fatigue all cause nausea by affecting the brain.

Other Symptoms

Nausea and vomiting are often associated with other signs and symptoms. Prolonged cases of vomiting can lead to symptoms of dehydration. Some other symptoms associated with nausea can be from the physiological reaction of the body to vomiting. Vomiting stimulates the vagus nerve, which leads to a decrease in pulse rate and blood pressure. That sudden drop in blood pressure sometimes causes a reciprocal adrenaline rush.

Adrenaline does several things to the body - such as increasing blood pressure and pulse - which includes pulling blood from the skin and triggering sweat. For that reason, victims of nausea and vomiting will often look pale with cool, clammy skin.

There are several options for treating nausea and vomiting, including over the counter (OTC) and prescription anti-nausea medications. Most importantly, treatment requires indentifying the cause of the nausea and addressing that condition.