Hellebore Poisoning in Dogs

Both plants of the Helleborus genus and the plants in the Veratrum family known as false Hellebore can be moderately toxic if eaten in large quantities. The unpleasant taste of these plants, particularly from the plants in the Helleborus genus, tends to prevent most animals from eating large enough quantities of the plant to become dangerously toxic. Although rarely fatal, ingesting large enough quantities of either plant can prove moderately noxious. The signs and symptoms of toxicity are very similar in both varieties of the plant even though the compounds causing the distress are somewhat different in nature.

Hellebore poisoning can refer to the moderate toxicity from either plants in the Helleborus genus, or from false hellebore, in the Veratrum family of plants.

Although plants in the genus Helleborus and the plants known as false hellebore (Veratrum viride or album) show similar symptomatology when ingested, the chemicals responsible for the reactions are divergent.  

• Abdominal pain
• Depression
• Diarrhea
• Difficulty breathing
• Excessive drooling
• Excessive thirst
• Heart rhythm abnormalities
• Lethargy
• Low blood pressure
• Paralysis
• Pawing at mouth (due to burning or tingling sensations)
• Seizures
• Sudden death
• Vomiting 
• Weakness

The sap from these plants may also cause minor skin irritation in either humans or other animals. This irritation usually clears up in just a few minutes. 

Types

The Helleborus genus of plants contains approximately twenty species in the family of Ranunculaceae. Some of the more common names for the plants of the Helleborus genus include: 

• Bear’s foot
• Black hellebore
• Christmas rose
• Corsican hellebore
• Easter rose
• Lenten hellebore
• Lenten rose
• Oriental hellebore
• Setterwort
• Stinking hellebore

Veratrum album is generally referred to simply as white hellebore or European white hellebore, and veratrum viride is called green hellebore or Indian hellebore. Both varieties have been labeled as false hellebore. Occasionally you will hear green hellebore labeled as Indian poke, although that name is more often used to denote the phytolacca acinosa plant, a type of pokeweed.

Plants in the Helleborus genus are from the Buttercup family (Ranunculaceae), but the Veratrum album and the Veratrum viride plants from the lily family (Liliaceae) are also denoted as white and green Hellebore. 

Hellebore (Helleborus)- An evergreen plant in the buttercup family. All plants in the buttercup family contain various cardiac glycosides as well as ranunculin, a glucoside. Ranunculin breaks down into the toxin protoanemonin in the digestive system. The most common variety seen is the Black hellebore (Helleborus niger), or the Christmas rose. 

Green Hellebore (Veratrum viride)- A perennial herb of the lily family which contains steroidal alkaloids that can cause cardiac failure if ingested in high enough doses. Toxins in these plants are generally only a problem during times of new growth. 

White Hellebore (Veratrum album)- Another variety of Veratrum plant with the Hellebore nickname, it also contains the toxic alkaloids. The concentration of alkaloids in white hellebore may be greater than the concentration in green hellebore. 

When consumption of the Hellebore plant is witnessed, then the initial diagnosis will be based on the identification of the plant combined with the symptoms. Reactions to these plants are generally fairly mild unless large amounts of the plant are eaten. If the reaction is severe enough to warrant a visit to the veterinarian’s office a sample of the plant should be brought with you to confirm the identification, particularly as there are multiple plants going by the same common name of Hellebore. If the symptoms and signs are incongruent with either Helleborus or Veratrum toxicity, or if the eating of the plant was unwitnessed then diagnosis may be more involved.

Your veterinarian may need to get a history of your pet’s health as well as information about any opportunities for inappropriate eating that may have occurred as well as information about any medications or supplements your pet may be on.  Drugs such as steroids, beta-blockers, and some chemotherapy agents may interact negatively with the cardiac glycosides present in the Helleborus genus plants. Your veterinarian will generally order a biochemistry profile, complete blood count, and urinalysis this time as well, with an emphasis on heart function and rhythm. Tests to check the functionality of both the liver and kidneys are also helpful in determining if any damage has occurred to either organ.

Prognosis will be dependent on how long it has been since the plant was ingested, how much was consumed, and what symptoms are presenting. A thorough rinsing of the mouth is recommended if your pet is showing signs of pain or swelling in the mouth. If it has been less than a few hours, and the amount eaten was not overly large, you may be instructed on how to properly induce vomiting in your dog using hydrogen peroxide. If large quantities of the plant were consumed, or if serious symptoms are starting to develop, your pet will need to visit the veterinarian’s office for further treatment. Gastric lavage is often recommended to void the various toxins from the patient’s system, after which activated charcoal is utilized to soak up as many of the remaining toxins as possible.

Supportive measures such as IV fluids are required to fight dehydration as well as ensure that the proper sugar and electrolyte balances are maintained. Calcium as an additive to IV fluids should be avoided with poisoning caused by Helleborus as calcium tends to enhance the effects of the cardiac glycosides. If symptoms of cardiac involvement are present then antiarrhythmic drugs such as atropine sulfate, procainamide or lidocaine may be used to regulate the heart rate.

Severe toxicity is rare due to the unpleasant taste and possible burning and itching in the mouth, particularly with the Hellebore plants that are in the Helleborus genus. Most symptoms from sampling these plants will dissipate within 24 hours. If the quantities ingested required a stay at the veterinary hospital, the recuperating patient should have a quiet, calm setting to return home to in order to speed recovery. This is of particular concern if the heart was affected due to cardiac glycoside involvement as further stress on the heart should be avoided. Anesthesia given to facilitate gastric lavage may cause short-term difficulties with coordination, and in that case, your dog may be confused and disoriented when they first return home.