Defensive vomiting

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Defensive vomiting refers to the use of emesis to defend against ingested pathogens or, in animals, against predators.

In Humans[edit]

Vomiting serves an evolutionary purpose for humans by preventing the ingestion of something harmful, and by expelling noxious substances once ingested.[1]

Vomiting excessive amounts of alcohol is an attempt by the body to prevent alcohol poisoning and death. Vomiting may also be caused by other drugs, such as opiates, or from toxins found in some foods and plants. Food allergies, such as lactose intolerance, can cause vomiting.[2]

Even morning sickness, nausea and vomiting common to most pregnant women but no other mammals, has a defensive purpose. Morning sickness discourages pregnant women from eating meat and strong-tasting vegetables, which may contain toxins and microorganisms. If ingested, the fetus might be harmed. After around the 18th week, the fetus becomes less vulnerable.[3]

In Animals[edit]

Turkey vultures will vomit to dispel any disturbing animal. They can propel their vomit up to 10 feet.[4]

The European roller, a much smaller bird found in parts of Africa, Europe, Asia, and the Middle East, uses vomit in a different way. A baby European roller will vomit a foul-smelling orange liquid onto itself to turn away a predator. The smell also warns the parents to return to the nest.[5]

See also[edit]


  1. ^ "Why rats don't vomit". Retrieved 13 October 2014.  External link in |website= (help)
  2. ^ "Nausea and vomiting causes". The Mayo Clinic. Retrieved 13 October 2014. 
  3. ^ Lang, Susan (June 25, 2008). "Morning sickness is pregnancy 'wellness insurance,' says Cornell professor". Cornell University. Cornell Chronicle. Retrieved 13 October 2014. 
  4. ^ "Turkey Vulture". Washington Nature Mapping Program. Retrieved 13 October 2014. 
  5. ^ ""Vomit Bird" Throws Up a Defense Against Predators". Discovery News. Discovery Channel. Retrieved 13 October 2014.