What Happens in a Dog's Body with Severe Vomiting?

by Jennifer Coates, DVM

We all know that vomiting is bad, but many dog owners don’t understand exactly how much damage severe or prolonged vomiting can do to a dog’s body.


Severe vomiting causes direct loss of water from the body but equally important is the fact that it prevents dogs from holding down and absorbing water that they try to drink to correct the problem. This combination quickly leads to dehydration, particularly if it is accompanied by diarrhea.

Dehydration has damaging effects throughout the body including:
  • Abnormal mental activity leading to confusion, depression, etc.
  • Inability to form tears, which can cause corneal damage
  • Low blood pressure that can result in organ damage and failure (especially the kidneys)
  • Gastrointestinal bleeding
  • Seizures
  • Permanent brain damage

Dehydration can cause shock and death when a dog’s blood pressure becomes so low and the blood becomes so thick (viscous) that adequate amounts of oxygen and other vital substances cannot be delivered to tissues throughout the body.

Electrolyte Loss

Sodium, potassium, chloride, calcium, magnesium, bicarbonate, and phosphate are examples of electrolytes without which cells cannot function normally.

Profuse or prolonged vomiting results in a significant loss of electrolytes. Electrolytes play many roles in the body. For instance, sodium is needed to generate the electrical signals that allow parts of the body communicate with one another and potassium helps regulate heart rhythm.

Acid-Base Imbalances

Vomit contains gastric acid, which is made, in part, of hydrogen ions. Losing hydrogen ions causes the body to become more alkaline. Since chemical reactions are designed to take place in a relatively narrow range of pH, alkalosis (as this condition is called) has a widespread effect.

The most obvious symptom is often muscle twitches. Interestingly, the body tries to compensate for alkalosis by slowing down breathing. This leads to an accumulation of carbon dioxide in the blood stream, and since carbon dioxide is an acid it can help correct the body’s pH.

Aspiration Pneumonia

The tube that leads to the lungs (the trachea) lies right next to the opening through which vomit enters the mouth. The epiglottis is designed to prevent anything other than air from entering the trachea, but it doesn’t always perform perfectly in cases of extreme vomiting. The presence of vomit in the lungs is irritating, interferes with the normal exchange of oxygen and carbon dioxide, and provides the perfect environment for a bacterial infection to flourish.

Damage to the Esophagus

Stomach acid is powerful stuff. The lining of the stomach is built to handle it but the esophagus is not. When the relatively delicate lining of the esophagus is repeatedly exposed to stomach acid it becomes inflamed and may develop ulcerations, both of which can subsequently interfere with its ability to move food and water into the stomach. Sometimes dogs will begin to regurgitate due to this esophageal damage after they have stopped vomiting.

Occasionally, the damage can be so severe that it results in a tear in the esophagus. This allows vomit and other material to flow into adjacent parts of the body. Esophageal tears are fatal without aggressive treatment.

The take home message? Severe or prolonged vomiting always warrants a veterinary visit.


Jennifer Coates, DVM graduated with honors from the Virginia-Maryland Regional College of Veterinary Medicine in 1999.  In the years since, she has practiced veterinary medicine in Virginia, Wyoming, and Colorado.  She is the author of several books about veterinary medicine and animal care, including the Dictionary of Veterinary Terms: Vet-speak Deciphered for the Non-veterinarian

Dr. Coates has recently joined the PetMD team and she is now writing for the Fully Vetted column; great blog, do check it out.

Jennifer also writes short stories that focus on the strength and importance of the human-animal bond and freelance articles relating to a variety of animal care and veterinary topics.  Dr. Coates lives in Fort Collins, Colorado with her husband, daughter, and pets.

Articles by Dr. Coates:
Kidney Disease – Say What? 
What Happens In The Dog's Body When The Kidneys Fail To Function Properly? 
Heat Stroke: What Happens In The Dog's Body?  
The Perplexities of Pancreatitis
The Other Side Of The Coin: The Cost Of Defensive Medicine
To Neuter Or Not To Neuter… That Is The Question
Don’t Forget the Physical Therapy
Common Misdiagnoses (Part 1)
Common Misdiagnoses (Part 2)
Picking the Right Dog to Breed
When Is It An Emergency?
Dog Allergies: Common, Commonly Misdiagnosed, or Both? 
Why Does The Spleen Get No Respect?
Protect Your Dog From Snake Bites 
More Creepy Crawlies
Why I Dislike Inflammatory Bowel Disease
Salmonella – A Significant Problem, Or Not? 
What’s In the Vomit?
Cortisol: What Happens In A Dog’s Body When It Goes Awry?
What Happens In The Dog's Body With Zinc Toxicity? 
What Happens In The Dog’s Body: Xylitol Poisoning 
What Happens In The Dog's Body: Insulin 
When Is Hypothyroidism not Hypothyroidism?

Related articles:
Symptoms to Watch for in Your Dog: Vomiting

Do you know what your dog is telling you about their health?

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An award-winning guide to better understanding what your dog is telling you about their health, Symptoms to Watch for in Your Dog, is available in paperback and Kindle. Each chapter includes notes on when it is an emergency.


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