Dog Fennel Poisoning in Horses

Dog Fennel Poisoning in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost
Dog Fennel Poisoning in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

What is Dog Fennel Poisoning ?

Ingestion of dog fennel by your horse can cause him to have various issues.  In a short amount of time, it can cause a dermatitis issue or diarrhea.  If he ingests this plant over a longer period of time, it can cause internal bleeding tendencies you may not even realize until it is too late.  There are many objects and plants that can cause some of these symptoms in your horse, but only a few cause contact dermatitis and bleeding tendencies.  Your veterinarian will be able to offer him supportive therapy and treatment in response to his symptoms.  If caught and addressed early, your horse should recover without any long term side effects.

Ingestion of dog fennel can be poisonous to your horse.  If you witnessed him eating this plant or suspect he has, contact your veterinarian.

Symptoms of Dog Fennel Poisoning in Horses

Symptoms of poisoning may include:

  • Increased urination
  • Diarrhea
  • Contact dermatitis 
  • Anorexia 
  • Allergic reaction 
  • Bleeding tendencies 


The dog fennel plant belongs to the Compositae family with the scientific name of Achillea millefolium.  This plant is also known as the dog daisy or mayweed.  Depending on the region, this plant can be found in the summer and sometimes in the winter.  It flourishes in many types of soil leading it to be found in many climates and regions of the world.  The plant is said to have a disagreeable odor leading many animals to avoid it.  The plant produces a flowering head or white and yellow and similar to a daisy.



Causes of Dog Fennel Poisoning in Horses

The volatile oil produced by the dog fennel plant is what is toxic to your horse.  The oil is made up of bisabolol, chamazulene, anthemic acid, and tannic acid.  Each individual oil can cause different effects on your horse.  Also, keep in mind just because it bothers one horse, it may not affect another.  Each oil produced by this plant can be used as an alternative medicine in the proper amounts and via the proper route.  However, when exposed to a larger amount it will have a negative effect on your horse.



Diagnosis of Dog Fennel Poisoning in Horses

Your veterinarian will begin by conducting a full physical exam on your horse.  She will make note of all of his symptoms, ask you when each symptom began and if they have been progressing.  If he is suffering from contact dermatitis or any other skin reaction, she may take a skin scraping or imprint sample to check for other causes.  She will need to rule out mites, infection, allergies, and other issues that can cause a similar symptom.

The vet will want to perform lab work so she can check the organ function of your horse and levels in his blood.  She will suggest a complete blood count (CBC) and chemistry panel to check for abnormalities.  Depending on the results, she may want to run more detailed blood related tests for additional diagnostic information.  If she suspects his symptoms are from a toxin, she may do a blood toxicology test if available.  If she notices his red blood cell count is low or abnormal she may run other tests to check for bleeding abnormalities.  She will want to rule out internal injury, parasitic infection, and organ system injury or failure.

If diarrhea is an issue, she may want to collect and inspect a fecal sample.  There are multiple tests she can do to rule out parasitic infection that may be the cause of the diarrhea or abnormal red blood cell count.  In regards to increased urination, she will likely collect a sample to run diagnostics on it.  A urinalysis can offer the veterinarian a lot of information on your horse’s urinary tract health.



Treatment of Dog Fennel Poisoning in Horses

While there is no antidote to dog fennel poisoning, your veterinarian can provide your horse with supportive care.  She can administer medications and supplemental therapies in response to the symptoms he develops.  She may want to start him on fluid therapy in an attempt to keep his urinary system flushed and to prevent the diarrhea from causing dehydration.

Depending on the appearance of his skin, she may administer medications to address it.  She may prescribe medications to be given orally in addition to medications to be applied topically, such as a spray or ointment.  If he is very itchy or has developed a secondary skin infection, she may also administer an antibiotic and a medication to calm the itching.

Each case of dog fennel poisoning is different so medications and therapies administered will vary.  It will all be determined by his symptoms and the therapies your veterinarian has available to her.  The main thing you need to do is remove your horse from the plant source to prevent further ingestion.



Worried about the cost of Dog Fennel Poisoning treatment?

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Recovery of Dog Fennel Poisoning in Horses

If caught and treated properly in a timely manner, your horse should recover from the dog fennel poisoning.  If he has a skin reaction and it goes untreated, he can develop a secondary skin infection that would be even more difficult and costly to treat.  If he developed a bleeding issue and it goes unnoticed and therefore untreated, it could lead to severe anemia, complications and could possibly be fatal.  Preventing your horse from ingesting this plant is ideal.



Dog Fennel Poisoning Questions and Advice from Veterinary Professionals

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