Holly Poisoning in Dogs

Ilex genus of plants, more commonly known as holly plants, are found throughout the temperate and subtropical regions of the world. Often used as an ornamental plant due to the glossy, dark-green leaves and attractive red berry-like drupes, it is an especially popular decoration around Christmas time. Although ingestion is generally not fatal, consuming several leaves or berries are likely to cause gastrointestinal distress, such as vomiting and diarrhea. The small spikes present on each leaf often prevent your pet from ingesting large amounts, but they can also cause pain and swelling in the mouth area when chewed.

Holly plants are often used as ornamental plants, especially around Christmas time. Ingestions of this plant, though rarely fatal, may cause severe mouth pain, vomiting, and diarrhea.

Although both the leaves and berries contain the moderately noxious compounds that cause the gastrointestinal upset, the spines on the leaves of the holly plant usually dissuade most canines from eating large enough quantities to cause serious damage.

• Diarrhea
• Excessive drooling
• Head shaking
• Loss of appetite
• Pawing at mouth 
• Spots of blood in mouth
• Vomiting 

Types 

There are around 400-600 species of holly plant in the ilex family. Some of the more common varieties used for ornamentation include:

American Holly (Ilex olpaca)- Native to eastern and south-central areas of the United States. It has bright red berry-like drupes and the leaves of the American Holly are conspicuously less shiny than its English cousin.

English Holly (Ilex aquifolium)- Also known as European holly, Christmas holly, and common holly, this variety is native to western and southern Europe, northwest Africa, and southwest Asia. It has bright red or yellow berry-like drupes, and shiny leaves with a leathery feel.

Japanese Holly (Ilex crenata)- Popular as a bonsai plant, this species is native to China, Japan, Korea, Sakhalin, and Taiwan, and is also known as the box-leaved holly. It has black berry-like drupes, and glossy, dark-green leaves.

The holly plant contains small quantities of several chemicals and compounds that can be mildly to moderately toxic to your companion. Some of the naturally occurring toxins that can be found in the holly plant are:

• Caffeic acid
• Caffeine
• Caffeoyl derivatives
• Chlorogenic acid
• Feruloylquinic acid
• Ilicine
• Ilexanthin 
• Kaempferol
• Quercetin
• Quinic acid
• Rutin
• Tannins
• Theobromine

The spikes on the leaves of most holly plants will cause initial symptoms to show up almost immediately as the discomfort will cause excessive drooling and pawing at the mouth. In those cases, identification of the plant may be all that is needed to diagnose the cause of the trouble. If only a small amount is ingested, further symptoms may not develop, larger amounts may cause gastrointestinal symptoms begin within thirty minutes of ingestion, or may be delayed for a few hours. In the event that your pet has consumed several leaves or berries, or the symptoms that are being displayed are more extreme than expected, your veterinarian may recommend that you pet visit the office. The veterinarian will interview you about any inappropriate grazing opportunities in addition to any concurrent supplements or prescriptions that your dog is on. A complete blood count, biochemistry profile, and urinalysis will be done to ensure there are no underlying toxins or disorders that need to be addressed, and any vomit will be examined for any plant materials or other inappropriate eating.

In many cases, treatment of holly plant ingestion can be handled at home with relative ease. It is important to contact your veterinarian before starting treatment to determine if either the amount eaten or the reaction to the toxin warrants a visit to the veterinarian’s office. Depending on how long it has been since ingestion, your veterinarian may instruct you on the proper technique to induce vomiting in your dog. Flushing of the toxins and any plant material from the mouth will help prevent further damage from swallowing the irritants. Once the plant material has been cleared from the mouth area, you will need to ensure that clean, cool water is available to ease mouth pain and to replace any fluids lost due to any vomiting or diarrhea. If a sizeable amount of the leaves or berries were ingested a visit to the veterinarian’s office for supportive therapy is generally recommended. Supportive therapy will include IV fluid treatment to prevent any dehydration or electrolyte imbalances as well as monitoring of the heart. Poisoning from the holly plant is rarely severe enough to require a full gastric irrigation, however, activated charcoal may be administered to absorb any toxins still present in the stomach and anti-inflammatory medications may also be used to reduce swelling.

The prognosis from holly toxicity is usually quite good, but removal of the plant from the environment is recommended to prevent further events. Fatalities usually only occur in cases of dehydration caused by excessive vomiting or diarrhea, so it is essential to ensure that your pet has sufficient access to clean water during recovery. The chemical theobromine, the toxic principal in chocolate, is also present in holly leaves, though in very small concentrations. If very large amounts of the leaves or berries were ingested, it is important to watch for signs of theobromine poisoning as signs may be delayed for several hours to a few days.