Matchheads contain potassium chlorate, a chemical that is toxic to dogs in large doses. Potassium chlorate is an oxidizer that makes fire burn faster and hotter. On the matchhead, it is combined with phosphorus sulfide which is easily ignited at low temperatures. Your dog would have to eat a lot of matches for severe poisoning to take place, so matches are traditionally considered non-toxic. The lowest lethal dose of potassium chlorate is 1200 milligrams per kilogram of your dog’s weight. A book of paper matches contains about 110 milligrams of potassium while 20 wooden matches contains about 330 milligrams. Dogs often like to chew on matchsticks and may end up licking the head off. Typically there are no symptoms, however dogs that ingest a book or more of matches might have gastrointestinal upset, abdominal pain, and diarrhea. In rare cases, dogs can ingest enough matchheads to have potassium chlorate toxicity. This can be serious as the oxidizing potassium chlorate causes methemoglobinemia, a condition in which there is an abnormal amount methemoglobin, a particular type of hemoglobin, in the blood. Affected animals could have hemolysis (ruptured red blood cells), low blood pressure, difficulty breathing and CNS symptoms. Untreated potassium chlorate causes severe kidney failure and eventually death, however, this is very unlikely to happen through match ingestion.

Matchheads contain a very small amount of a toxic chemical called potassium chlorate. Dogs can safely ingest small amounts of matches, but very large doses could cause gastrointestinal upset and CNS symptoms. Match poisoning in dogs is very rare.

These are the symptoms you might see in a dog with potassium chlorate toxicity after ingesting a very large number of matches.

There are two common types of matches, both of which contain potassium chlorate.

Although it is rare, match poisoning can occur. These are some of the risk factors.

If you think your dog may have ingested a large number of matches it’s a good idea to call the veterinarian and ask for instructions based on your dog’s breed and weight. The veterinarian will want to know the amount you think your dog ingested. In most cases, the veterinarian will merely recommend you observe your dog for symptoms. If there is a possibility that a very large amount was ingested, the veterinarian may recommend you bring your dog in for further examination.

The veterinarian will perform a physical examination and check your dog for CNS symptoms, like lack of coordination, and tremors. If methemoglobinemia is present it can be diagnosed with a blood test which will show abnormal protein levels as well as a low red blood count. In the advanced stages, bloodwork and urinalysis may also show kidney and liver dysfunction.

In most cases, no treatment is recommended for match ingestion. Small doses will pass through the gastrointestinal tract and be excreted in the feces without harming your dog. Clinically affected dogs will be treated symptomatically. Medication may be prescribed to help control tremors, seizures, and low blood pressure. Methemoglobinemia can be treated with injections of methylene which will help to normalize the proteins in your dog blood. In very severe cases, a blood transfusion might be needed to replace damaged red blood cells.

Most dogs make a full recovery from match ingestion and many will have no symptoms at all. If match poisoning with potassium chlorate toxicity does take place, this can usually be treated successfully, unless there is a delay in treatment and damage to the liver or kidneys is already present. Match poisoning can be managed by buying matches in small quantities. If you do need to store a lot of matches for some reason, ensure they are kept in a sealed plastic container that your dog cannot access. This is especially true if your dog is small and likes to chew on things.