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Irritable Bowel Syndrome (IBS) in Dogs
Revised: March 07, 2023
Published: March 21, 2005

Grey dog resting on front paws

The signs of inflammation in the colon (also called the large intestine) are the same regardless of the cause: gooey, mucous diarrhea, straining to pass stool, cramping, and sometimes a surprising urgency to "go." These symptoms can be acute, as is common with short-term stress like boarding, returning from boarding, or diet change, or they can be chronic, as with whipworm infection or inflammatory bowel disease.

Many people get confused between inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). IBD is a physical disease where the intestinal lining is infiltrated by inflammatory cells. The delicate intestinal lining becomes thickened, and it alters the absorption of nutrients. The infiltration can be seen under the microscope, which is how the diagnosis is confirmed. Inflammatory Bowel Disease is a completely different disease from Irritable Bowel Syndrome, so if you are looking for information on Inflammatory Bowel Disease, please click the link above.

IBS is a psychosomatic disease. It is the activity of the mind that causes the symptoms. Most people have had some kind of experience where stress has produced intestinal distress, be it cramping, nausea, diarrhea or all of the above.

Chronic anxiety can similarly result in chronic diarrhea. This is basically what IBS is all about. Intestinal biopsy results are normal because there is nothing directly wrong with the large intestine. The process is the same whether the patient is human or non-human.

Large intestinal diarrhea in veterinary patients can have many causes and IBS is afoot in about 10-15% of cases. It is important to rule out physical causes before blaming psychological reasons, but if all tests are normal and treatment for physical problems is not yielding results, this is when a biopsy is helpful. If after medication trials, diet trials, and diagnostic tests, including biopsy, are all normal, then it is time to consider IBS.

It should be noted that fresh blood in the diarrhea is common with large intestinal diarrheas but not so much with the large intestinal diarrhea of IBS.  Fresh blood in the diarrhea is a sign that there is a physical cause and not a psychosomatic cause. Knowing this can help direct the medical approach.

Treatment of IBS

Most commonly, IBS is addressed via the GI tract rather than via the psyche. Increasing dietary fiber is helpful to many IBS patients as fiber has been found to help normalize the spasms of the large intestinal muscles and many therapeutic high-fiber diets are sold through veterinary hospitals. If your pet finds these unpalatable, ask your veterinarian about how to add wheat bran or a commercial fiber supplement to a diet your pet prefers. There are presently several commercial dog foods that contain calming supplements. Using one of these plus a fiber supplement might cover both the fiber angle as well as the anxiety.

For many patients, cage rest or tranquilizers allows for enough rest to control symptoms. Antispasmodics or general anti-diarrhea medications such as loperamide, azulfidine, or metronidazole can be used on an "as needed" basis to control signs.

A number of supplements (not to mention pheromone products) have recently been marketed to address anxiety. These are not as strong as prescription drugs but are available without a prescription for those who wish to try them:  

  • Alpha Casozepine: This is a milk protein with natural calming properties. It is available as an oral supplement (Zylkene®) for pets or in special calming pet foods (Royal Canin Calm Diet®, Hills Urinary Stress C/d for cats®).

    L-Theanine: This is a derivative of green tea and is available in capsules as well as flavored chews (Anxitane®, Solliquin®, Composure®).

    Adaptil Defuser and Collars: Dog Appeasement Pheromone or D.A.P. is naturally secreted by mother dogs to communicate safety and security to her litter of puppies. This pheromone has been synthesized and is available as a room spray, plug-in wall defuser, and an impregnated collar that the dog can wear. This gives the anxious dog a message in his or her own language that there is nothing to be anxious about.

    Cannabinoids: These are obviously controversial and are not presently legal except as hemp products which may be appropriate. CBD is commonly marketed for pets, but at the present time, none of the recent legalization efforts have included pet products, and quality control is lacking.


A more aggressive approach might be addressing the anxiety with medications. The source of emotional stress may not be obvious, but general anti-anxiety medications such as amitriptyline, clomipramine, or fluoxetine may be of use, particularly if the anxiety source is not clear or cannot be removed. Some patients will respond to supplements as listed above. It is important to imagine the pet’s world from his/her own perspective. The pet does not speak English and must infer what is going on from events he or she witnesses directly. Inconsistent scheduling, moving to a new home, noisy construction nearby, or even weather changes can confuse an animal.

Consult your veterinarian if you wish to pursue one of these therapies. However, keep in mind that IBS is not diagnosed until a medical workup for physical causes of large bowel diarrhea has not shown any reason for illness.

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