Why Does My Dog Have Diarrhea and What Causes it?

Has your dog had loose stools lately? Are new dog treats causing loose stools or is it something more? Ever wonder what causes your dog to have diarrhea? This article is going to discuss and explain diarrhea, the difference between “normal” poop and diarrhea, what’s causing your dog to have diarrhea, and how to prevent diarrhea for your dog.

What is Diarrhea?

Diarrhea is defined as loose, unformed stools occurring three or more times throughout one day. If your dog even has just one episode of loose stools then technically it is not considered diarrhea. Instead it is considered a loose bowel movement. But, whether or not your dog has diarrhea or just one loose bowel movement, it is proof that your dog’s digestive system may be unhappy. Similar to humans, there are several reasons why your dog may be having digestive upset.




Diarrhea is easily identifiable. Formed stools should not have any mucus, blood, liquid, or undigested food. Although, undigested food may be seen if your dog ate something that is not easy to digest, such as corn or rubbish. Diarrhea has a liquid-like texture and it may vary in color from a bright yellow to black. Reds, grays, greens, and beige colors may also be seen. Each color can tell you a lot about what’s going in your dog’s digestive system.

Why Does My Dog Have Diarrhea?

What Causes Diarrhea?

The two main causes of loose stools are parasites in the intestines and a dietary allergy or response. Heart medication, de-wormers, antibiotics, pain medications and over-excitement/stimulation may also cause diarrhea. If your dog has to take medication and you think it may be the cause of your dog’s diarrhea, contact your veterinarian to see if you can change the prescription. If your dog must continue taking the medication that you think may be causing the diarrhea then you can try giving your dog a bland diet of white rice and lean ground beef to ease digestive upset.

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Parasites Causing Diarrhea

There are a few ways you can tell if your dog is suffering from parasites or if food is the culprit. Roundworms, hookworms, and thread worms are three types of worms that can infect your dog. These worms then cause infections. Roundworms, which can grow up to 7 inches long and lay hundreds of thousands of eggs, are the most common parasite. Roundworms are also known as whipworms. These parasites can cause an infection known as Trichuriasis in the tissue of the rectum, colon, and appendix. Hookworms are not seen as often because they typically like to be in hot climates with high humidity. Although they are not as common, hookworms are still extremely harmful. These worms, which grow between .25 and .5 inches long, latch onto the small intestines to absorb blood and tissue from the mucosa leading to malnutrition and blood loss. Threadworms, also known as pinworms, are especially harmful to humans because they can be transmitted from dogs to humans. The most common transmission occurs by coming in contact with an infected dog’s feces orally or through open skin.

Giaradia Causing Diarrhea

Dogs can also become infected with Giardia, which is not a worm but a parasitic species that causes intestinal infection. Some dogs may not even have symptoms, such as diarrhea, while being infected with Giardia. If you suspect an illness and your dog is not having any obvious symptoms, take note of normal daily activity and eating habits. The feeding form of Giardia remains in the infected dog’s intestines while the cystic form of Giardia is passed through the dog’s feces. This cystic form can infect any dog that ingests, licks, or sniffs the feces. The parasite may also be transferred through infected water.

Acquiring Parasites

There are several ways dogs can acquire these parasites. Parasites may be transferred in the uterus of the mother during pregnancy, through the mother pup’s milk, through open- skin contact (like the paws), ingesting the feces directly, and through dirt or water infected with larvae. Parasites can cause several symptoms, with diarrhea being the most prevalent. Symptoms also include abdominal pain, weakness, dehydration from the loose stools, and tiredness. Homes with infected dogs should be sanitized regularly and properly. Here are a few important steps to take.

Precautions for Parasites and Infection

  1. Infected dogs should be secluded from other pets, especially cats and dogs since they are easily susceptible to getting parasites.
  2. Always wear gloves, use a scooping device and a clean waste bag when cleaning up your dog’s feces from the yard or sidewalk.
  3. If your dog has loose stools inside your home immediately clean the feces and sanitize the area with a proper disinfectant cleaning solution.
  4. Dispose of the feces so no other humans or animals can come in contact with the parasites and infection.
  5. Change your dog’s water regularly so the water cannot become contaminated.
  6. Wash your hands! Parasite larvae (eggs) are sticky so they can stick on clothing, hands, and shoes after stepping in the dirt where your dog relieved him/herself.

Immediately visit your veterinarian if you think your dog may have a parasite or infection. A de-wormer or antibiotic may be prescribed and then regular heartworm medicine may be suggested.

Dietary Upset Causing Diarrhea

Dietary upset can also be the cause of acute loose stools as well as diarrhea. If your dog is a scavenger, as many dogs naturally are, you may find him or her eating garbage, grass, plants, wood, decaying food or animals, and plastic. It’s unlikely that your dog will be able to digest these items and in that case vomiting may be present even before attempting digestion. Certain foods, which may appear harmless, may cause diarrhea if your dog has an intolerance or an allergy. With both allergies and an intolerance your dog may experience vomiting, stomach pain, and diarrhea. The additional allergy symptoms allow you to rule out a food intolerance. Food allergies more commonly display signs of trouble breathing, rashes, and itching. Your dog may have an intolerance to a number of ingredients commonly found in dog food and treats, which include eggs, corn, beef, wheat, chicken, spices, and soy. If you think your dog may have an intolerance to one of these foods you should try removing any possible culprit from your dog’s diet and then slowly start to reintroduce each food. While you reintroduce each food, keep a journal of your dog’s reactions. If you are unsure which foods are typically safe for dogs, check out What Can I Feed My Dog? for a list of commonly safe foods. Always consult a veterinarian before implementing any changes to your dog’s lifestyle.

What Diarrhea Can Tell You

The color, texture, frequency, and odor of your dog’s diarrhea all say a lot about what’s going on. Red and black feces can indicate bleeding in the lower and upper GI tract respectively. Watery, yellow, gray or green feces may indicate digestion happening too quickly. If the feces have a distinct smell of a certain food then this may also indicate quick digestion. Beige shades may indicate a lack of bile. Bile is produced by the liver and stored in the gallbladder. It aids in digestion by helping break down fats into fatty acids. Foamy stools may indicate a bacterial infection while shiny or oily stools may indicate mal-absorption.

Kimberly Mattar
August 20th, 2014
Latest Update: May 16th, 2019