Dangers of Milk Thistle to Canines

Updated November 21, 2016

Milk thistle is an herb most often used for detoxification. This herb is used in humans and dogs alike to rid the body of toxins from medications and illness as well as to promote growth of new and healthy tissue. Milk thistle is a natural way to relieve the effects of liver disease, pancreatic problems and even skin problems in dogs. It does not come without potential dangers to your dog, however.

Supressed Liver Function

Milk thistle, when given as advised by a veterinarian, is excellent for keeping the liver cleansed and performing at peak condition. When given too often, for example as a daily supplement, milk thistle can suppress liver function. This results in a liver that performs inconsistently, and could lead to illness in your dog.

Pregnancy Complications

While no tests have been conducted to determine whether milk thistle is dangerous for pregnant dogs, milk thistle is not recommended for use by pregnant women. Milk thistle could cause serious complications in a dog's pregnancy, therefore should probably be avoided unless directed by your veterinarian.

Digestive Problems

When administered improperly, milk thistle can cause digestive disturbances in dogs. Dosages of milk thistle that are too high often cause loose, runny stools or cases of diarrhoea in dogs.

Strength Variations

Different brands of milk thistle may have differences in the potency of the herb. They may come in various concentrations and strengths, even if the dosage is the same. This can result in dangerous side effects (liver dysfunction, digestive dysfunction) in dogs. Use a brand recommended by a veterinarian to avoid this.


As with any medication or herbal supplement, your dog may experience allergies to milk thistle. The allergy may be minor, such as slight skin or digestive irritation, or severe, such as impaired breathing. Stop use of milk thistle immediately in the case of allergies.

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