Is mistletoe poisonous to dogs? Yes. The ASPCA lists American mistletoe as toxic to dogs, cats and horses, with vomiting, diarrhea, difficulty breathing and a low heart rate among the signs. The FDA says its toxins "affect the heart, causing low blood pressure and slowed heart rate." Holly is also listed as toxic to dogs. If your dog has eaten mistletoe leaves, stems or berries, or any part of a holly sprig, call your vet, the ASPCA Animal Poison Control Center (888-426-4435) or the Pet Poison Helpline (855-764-7661) now.
If Your Dog Ate Mistletoe or Holly: What to Do Right Now
- Call for advice first. Phone your veterinarian, the nearest 24-hour emergency animal hospital, the ASPCA Animal Poison Control Center at 888-426-4435, or the Pet Poison Helpline at 855-764-7661. Both poison lines answer 24 hours a day, and a consultation fee may apply.
- Do not make your dog vomit and do not give any home treatment, food or medicine, unless a veterinarian or poison-control specialist tells you to for this exposure, at this moment. Our guide on whether you should make your dog throw up explains why that decision belongs to the vet.
- Go to an emergency vet immediately if your dog is weak, stumbling, collapsing, breathing with difficulty, or having a seizure.
- Work out what was eaten. Leaves, stems, berries or a whole sprig? Real plant or artificial decoration? Count what is missing if you can.
- Have the details ready: the plant or a photo, the time, and your dog's age, weight, breed and health conditions, including any heart condition.
How mistletoe or holly affects a dog depends on the individual animal's size and health and on what and how much was eaten. Only a veterinarian can judge that. This article is general information, not a diagnosis.
Is Mistletoe Poisonous to Dogs? What the Sources Say
The sources we read agree that mistletoe is toxic to dogs. They differ in how they describe the severity, and that difference is worth understanding.
- The ASPCA lists American mistletoe (Phoradendron flavescens) as toxic to dogs, cats and horses. It names toxalbumin and phoratoxins (lectins) as the toxic principles, and lists "vomiting, diarrhea, low blood pressure (rare), difficulty breathing, low heart rate."
- The the FDA, in a holiday safety page dated February 2025, says "the major toxic chemicals in mistletoe are lectins and phoratoxins," which affect the heart. It adds that "severe mistletoe toxicity is uncommon and usually only occurs if your pet eats a large amount."
- The Pet Poison Helpline says eating American mistletoe "commonly results in gastrointestinal distress (e.g., vomiting, diarrhea), but large ingestions of this plant may lead to low blood pressure with stumbling gait."
- The Merck Veterinary Manual (Houseplants and Ornamentals Toxic to Animals, reviewed by Renee D. Schmid, DVM, of Pet Poison Helpline, last updated September 2024) describes toxic proteins "in all parts" and, after a toxic dose, "vomiting, profuse diarrhea, dilated pupils, rapid labored breathing, shock, and death from cardiovascular collapse within hours."
Why "Usually Mild" Is Not a Reason to Wait
Read together, these sources describe a plant that most often causes stomach upset but that can, in some cases, affect the heart and circulation. Merck describes the serious outcome as developing "within hours" of a toxic dose.
The trouble is that an owner at home cannot tell which kind of case they have. You usually do not know exactly how much was eaten, and "a large amount" means something different for a small dog than for a large one. None of the sources gives a figure an owner could use to decide, and this site does not publish one. That judgment belongs to your vet or a poison line, who can weigh the exposure against your dog's size and health.
It also matters that a dog can look normal at first. Our guide to what to do when your dog ate something toxic but seems fine explains why that is still a reason to call.
Signs of Mistletoe Poisoning in Dogs
These are the signs named by the sources above, listed so you can report them accurately, not so you can decide at home whether your dog is affected.
| Source | Signs it lists |
|---|---|
| ASPCA | Vomiting, diarrhea, low blood pressure (rare), difficulty breathing, low heart rate |
| FDA | Vomiting and diarrhea in dogs and cats, difficulty breathing, weakness (from low blood pressure or slowed heart rate), odd behavior |
| Pet Poison Helpline | Vomiting and diarrhea; after large ingestions, low blood pressure with stumbling gait |
| Merck Veterinary Manual | After a toxic dose: vomiting, profuse diarrhea, dilated pupils, rapid labored breathing, shock, cardiovascular collapse |
Weakness, stumbling, collapse and breathing difficulty are the signs that mean go to an emergency vet now, not wait for a callback. For the general picture of what to watch for, see our guide to signs of poisoning in dogs.
Is Holly Poisonous to Dogs?
Holly is the other half of the classic December doorway, and it is also listed as toxic to dogs.
- The ASPCA lists holly (Ilex opaca, also called American holly, English holly, European holly, inkberry and winterberry) as toxic to dogs, cats and horses. It names saponins as the toxic principle, lists "vomiting, diarrhea and depression," and describes the leaves and berries as "low toxicity."
- The FDA says "the main toxic culprit in holly leaves and berries is a group of chemicals called saponins," and lists "drooling, vomiting, diarrhea, loss of appetite, and decreased activity" in dogs and cats.
- The Merck Veterinary Manual notes that saponins, an alkaloid (theobromine), triterpene compounds and "unknown compounds with digitalis-like cardiotonic activity" have been found in holly leaves, fruits and seeds.
"Low toxicity" is the ASPCA's general description, not a promise about your dog. Holly berries are small and easy to swallow in numbers, and this site does not publish a count that is safe or unsafe. Call your vet or a poison line and tell them how many berries or leaves may be missing.
Mistletoe and Holly Side by Side
| Mistletoe | Holly | |
|---|---|---|
| Listed toxic to dogs (ASPCA) | Yes | Yes |
| Toxic principles named | Lectins, phoratoxins, toxalbumin (ASPCA, FDA) | Saponins (ASPCA, FDA) |
| Main concern the sources describe | Stomach upset; heart and circulation effects after large ingestions | Stomach upset |
| What to do | Call your vet or a poison line | Call your vet or a poison line |
The last row is the same for both on purpose. The differences between the plants are for the specialist to weigh, not a reason to skip the call.
"It's Been on the Door All December"
Decorations that hang for weeks drop things. Dried leaves, loose berries and sprigs that fall from a wreath or a doorway end up on the floor, where a dog finds them, often when nobody saw what happened.
- Check under doorways, wreaths and garlands regularly, especially as the plants dry out.
- Hang real mistletoe and holly high, well above the height your dog can reach standing on its back legs.
- Watch table centerpieces and gift arrangements. Holly and mistletoe are often mixed with other plants, and a dog on a counter or coffee table can reach them.
- Artificial decorations are not automatically safe to chew. Plastic berries, wire and ribbon are not a plant poisoning question, but a swallowed piece can still need a vet. Our guide to whether what your dog ate could cause a blockage covers that side.
- Save both poison line numbers in your phone: ASPCA Animal Poison Control Center 888-426-4435 and Pet Poison Helpline 855-764-7661.
Sources Checked
On September 27, 2026 we read the ASPCA Animal Poison Control Center's entry for American mistletoe and its entry for holly, and the U.S. Food and Drug Administration's holiday pet safety page. On the same date we read the Pet Poison Helpline's page on mistletoe and the Merck Veterinary Manual chapter on houseplants and ornamentals toxic to animals.
Frequently Asked Questions
Is mistletoe poisonous to dogs if they only eat the berries?
The ASPCA and Pet Poison Helpline treat the plant and its berries as toxic, and the Merck Veterinary Manual describes toxic proteins in all parts. Call your vet or a poison line whichever part was eaten.
What are the symptoms of mistletoe poisoning in dogs?
The sources list vomiting and diarrhea most often. The ASPCA and FDA also list difficulty breathing, low heart rate and weakness, and the Pet Poison Helpline mentions low blood pressure with stumbling after large ingestions. Weakness, stumbling or collapse need an emergency vet now.
How much mistletoe is dangerous for a dog?
This site does not publish amounts, because the answer depends on your dog's size and health and on what was eaten. The FDA notes that severe toxicity usually follows a large amount, but only your vet or a poison line can judge your dog's case.
Is holly poisonous to dogs?
Yes. The ASPCA lists holly as toxic to dogs, with vomiting, diarrhea and depression, and describes the leaves and berries as low toxicity. Call your vet or a poison line if your dog has eaten any.
Is artificial mistletoe safe for dogs?
It is not a plant poisoning risk, but plastic berries, wire and ribbon can still cause problems if swallowed. Keep all decorations out of reach and call your vet if your dog swallowed a piece.
This article is general information and does not replace veterinary care. If you think your dog has eaten mistletoe, holly or any holiday plant, contact your veterinarian, the ASPCA Animal Poison Control Center at 888-426-4435, or the Pet Poison Helpline at 855-764-7661 now. Toxicity varies with your dog's size and health, and only a veterinarian can assess your individual dog.