Perilla Mint Poisoning in Horses

Perilla Mint Poisoning in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

Most common symptoms

Poor Appetite / Weight Loss


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Most common symptoms

Poor Appetite / Weight Loss

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Perilla Mint Poisoning in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

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What is Perilla Mint Poisoning ?

Perilla mint is a weed found naturally in many areas.  It goes by numerous common names so while you may know it as perilla mint, other people may know it as rattlesnake weed or purple mint.  It is commonly found along wooded areas or waste lands but you should check for it anywhere on your pasture as a precaution.  If your horse ingests this plant, it will lead to respiratory distress and possibly death.  It is be a medical emergency as many horses do not survive after ingesting this plant. There is no antidote or cure so your veterinarian can only offer your horse supportive therapy and medications in response to his symptoms.  Even with medical intervention, prognosis of recovery is guarded.

Ingestion of perilla mint by your horse should be considered a medical emergency.  If you witnessed him ingesting this plant or notice he is having trouble breathing, contact your veterinarian immediately.

Symptoms of Perilla Mint Poisoning in Horses

Symptoms may include:

  • Respiratory distress
  • Cough
  • Tachypnea 
  • Increased body temperature 
  • Chronic weight loss


Perilla mint is identified by its square shaped stem and is most commonly found along wood lines and waste areas.  This plant produces small white flowers and gives off a minty fragrance.  Other common names this plant is known by include beefsteak plant, purple mint, purple perilla, common perilla, Chinese basil, wild basil, shiso, blueweed, Joseph’s coat, rattlesnake weed, and wild coleus.

Causes of Perilla Mint Poisoning in Horses

Perilla mint is scientifically known as Perilla spp.  Intoxication from this plant is not as common as other plants but has been reported to occur. This plant contains the toxin L-tryptophan which affects the respiratory system and nerve function and can cause death in just a few hours.  A horse can be affected by it via ingestion or even sometimes just inhalation.

Diagnosis of Perilla Mint Poisoning in Horses

Your veterinarian will begin by performing a full physical exam on your horse.  It will allow her to assess him as a whole and note all of his symptoms.  She will listen to his lungs via auscultation for any symptoms of distress and in which part of the lungs it is occurring.  She may want to take radiographs to rule out other possible causes such as pneumonia.

She will want to perform lab work so she can check his organ values and levels in his blood.  She will suggest a complete blood count (CBC) and chemistry panel to check for abnormalities.  The CBC and general chemistry panel can provide diagnostics on the general function or dysfunction of the internal organs in general.  

If your horse ends up dying, a necropsy is highly recommended.  In cases of perilla mint toxicity, the lungs will appear partially collapsed but the lining and structures may appear normal.  The presence of white foam in the airways is a common finding within the lungs themselves. With a proper diagnosis and proper culprit identified, you can then take steps to prevent this intoxication from happening to your other horses and animals.


Treatment of Perilla Mint Poisoning in Horses

You will need to remove your horse from the source of perilla mint plant immediately to prevent further ingestion.  There is no exact treatment your veterinarian can offer your horse.  She can provide supportive therapies and keep your horse comfortable.  She can offer medications and therapies in response to symptoms your horse develops.  For respiratory distress and related symptoms, she can administer corticosteroids, diuretics, atropine, antibiotics, and antihistamines as needed.  She may also offer him oxygen therapy to make it easier for him to breathe. 

When treating your horse, it is extremely important you keep him as calm as possible.  Causing your horse to stress can cause him to be anoxic and can kill him very quickly.  This can be very difficult for you and your horse.  This is when it may be helpful to have a veterinarian travel to you versus you bringing your horse to the veterinarian’s clinic. Other therapies will be provided as the veterinarian sees fit.

Recovery of Perilla Mint Poisoning in Horses

Recovery from perilla mint toxicity is considered guarded to poor depending on the severity of your horse’s symptoms.  In some cases, if the horse is able to survive the first hour of toxicity, his chance of recovery is higher than those that do not.  

Prevention of perilla mint toxicity is the best thing you can do for yourself as the owner and for your horse’s well being.  If you are unsure what plants you have on your pasture, take them to someone of knowledge to identify them.  It could be what saves your horse’s life.

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Perilla Mint Poisoning Questions and Advice from Veterinary Professionals