Colitis & Diarrhoea in Dogs and Cats

Colitis and diarrhoea are both conditions of the bowel involving diarrhoea or loose motions and warrant different types of treatment depending on the cause and symptoms.


Diarrhoea normally occurs as a result of upsets within the bowel, particularly the small intestine. This is the section of bowel directly after the stomach and is involved in the digestion and absorption of food.

Symptoms of diarrhoea can include:

  • A change in stool consistency – anything between soft and watery stools
  • A variation in the colour of the stools, including yellowish or clay coloured stools
  • An increase in the number of times that motions are passed
  • Stools which are foul smelling
  • The presence of blood (normally dark) in the stools

There are two types of diarrhoea, acute and chronic.

Acute diarrhoea occurs suddenly, only lasts a few days and is normally easy to clear up. However, some types of acute diarrhoea can be life threatening, especially those where blood is present or where dehydration could be an issue. If your dog or cat seems unwell, then seek help immediately. Causes of acute diarrhoea include

  • Overeating
  • Sudden changes to diet
  • Consumption of food which is decaying or inappropriate
  • Bacterial infections
  • Viral infections
  • Stress
  • Allergic reactions to food components

Chronic diarrhoea is a long-term problem where there has been either a continual problem or where a problem keeps coming back. Causes of chronic diarrhoea include:

  • Malabsorption, failure to absorb food properly
  • Pancreatic disease
  • Overgrowth of bacteria within the small intestine (SIBO)
  • Parasites
  • Food allergies
  • Inflammatory bowel disease (IBD)


Animals with acute diarrhoea should be starved for 24 hours to allow the bowel to rest and repair itself. Then feed a bland diet that is easy to digest. Foods that are low in fibre and fat are ideal. Lean white meat, fish and cooked eggs are suitable. Rice is a good carbohydrate source to add, as it is very easy to digest.

It is important to avoid all milk and milk related products and rich foods like liver or other offal. Once things return to normal, gradually reintroduce the old diet over a few days.

If your cat or dog is prone to bouts of diarrhoea then you should consider changing the diet to one of the following recipes:

Dogs – canned foods

Dogs – complete dry foods

Cases of chronic diarrhoea can only really be treated after a diagnosis has been established. Special enzyme supplements will be needed if pancreatic insufficiency is diagnosed.

If a dietary allergy or dietary intolerance is suspected, then you will need to organise an exclusion diet to help eliminate the cause or ask your vet for a blood test to identify possible allergens. Some of the more common allergens include wheat, beef, soya and dairy products although any food can become an allergen.


The colon is the last part of the large intestine extending from the caecum to the rectum. Inflammation of the colon is referred to as colitis and is a relatively common condition in dogs. Colitis is far less common in cats.

Symptoms of colitis can include:

  • Stools containing mucus or jelly-like material
  • Small stools, which are passed frequently
  • Fresh bright red blood in the stools
  • Diarrhoea or loose stools
  • Variable stool consistency, from complete liquid to solid or a mixture of both
  • More frequent passage of stools up to six times a day or more
  • Straining before, during and after stools are passed
  • Flatulence
  • Vomiting, fever, abdominal pain and weight loss in severe cases


Colitis can affect dogs or cats of any age, although some breeds of dog are particularly prone to this condition.

Common causes include:

  • Food allergies or dietary intolerance to specific food ingredients
  • Stress
  • Parasites, including hookworm and whipworm

Many cases of colitis are idiopathic in origin, meaning that the exact cause cannot be identified.


Once a diagnosis has been established, your vet may use a number of drugs to help control the symptoms. These include antibiotics and corticosteroids such as prednisolone. However, it is often possible to control the illness by other means.


Diet is now recognised as being of major importance in the long-term management of colitis. The following types of diet are known to help:

High fibre diets

The extra fibre in foods of this type will help regulate the passage of food through the gut and control the level of water present in the faeces. The following Denes products may be useful:

Dog – canned food

Dog foods – complementary

Alternatively, you can add extra fibre by adding bran flakes, oatmeal, wheatgerm or cooked lentils to any of our other canned recipes. For each 100 grams of food, add approximately 1 heaped teaspoon of fibre and mix in well.


  • Adding wheat bran or oat bran to the diet can help.

Highly digestible diets

Diets of this type leave a low stool volume, reducing faecal mass. Suitable Denes recipes include:

Dog food – canned

Cat food – Thrive Cans

Low allergy diets

Many cases of colitis are caused by dietary intolerance or allergy to certain components or substances in the food. Occasionally, this may be due to food additives. The most common food allergens that affect dogs are wheat gluten and beef. Chicken or fish sometimes causes problems in cats.

The following Denes products may help where food allergies are suspected:


Dog foods – canned

Cat foods – Thrive Cans


Dog foods – canned


Dog food – canned


In addition to dietary measures to help treat these conditions, herbal remedies can also be of value. The following products are useful:

  • Denes Respiratory Support (Garlic Oil) Capsules, Garlic is used to control the levels of bacteria in the gut by encouraging growth of friendly bacteria and inhibiting those which are not beneficial. It is a good remedy for helping with diarrhoea of any cause
  • Garlic also has some antispasmodic effect, helping relieve some of the tension in the bowel which arises during more severe colitis attacks
  • Denes Digestion Powder. This herbal supplement contains marshmallow root, agrimony, peppermint leaf, liquorice root, ginger root, slippery elm and Kaolin to help soothe the lining of the bowel and firm up the stools
  • Tranquil & Calm Powder. This herbal supplement is useful where psychological stress is a factor. Valerian, one of the ingredients, is an antispasmodic, helping to relax the bowel where straining is present
  • Denes Gut Health Probiotic Powder. The probiotics in this supplement will help support and stabilise the bacteria within the bowel. It is a good remedy for all types of diarrhoea and colitis
  • Denes Probiotic + Fibre Powder. The combination of probiotics and ground psyllium seed in this supplement will help support and stabilise the bacteria within the bowel as well as adding additional fibre to help firm up the stools. It is a good remedy for all types of diarrhoea and colitis
  • Denes Gas and Diarrhoea Support. The combination of probiotics and herbs in this supplement will help support and stabilise the bacteria within the bowel as well as absorbing gases and other nasties. It is a good remedy for all types of diarrhoea and colitis



With vomiting (gastroenteritis) Arsenicum album
With blood and foul smelling Arsenicum album
From rich food or change of food Nux vomica
From fatty food Pulsatilla
From getting wet or soaked through Rhus tox
If long-term Sulphur

Other useful Denes fact sheets to read: