Mayweed Poisoning in Dogs

The mayweed is native to Africa, Asia, and Europe, but can also be found in many areas of North America, Australia, and New Zealand along the side of roads, in fields, and in abandoned areas. Many people call it the stinking chamomile because it looks like a true chamomile plant, but it smells very unpleasant. The plant itself looks like a weed and has a flower that looks like a daisy with white petals and a yellow center. Even though it is not a true chamomile plant, they both have the same toxic properties, which are the volatile oils bisabolol, chamazulene, anthemic acid, and tannic acid.

Mayweed poisoning is a moderately serious condition caused by the consumption or exposure to any portion of the mayweed. The dangerous chemicals in the mayweed are anthemic and tannic acids, chamazulene, and bisabolol, which are volatile oils. These may have mild reactions like contact dermatitis from skin exposure to more serious symptoms, such as bleeding disorders and anaphylactic shock due to allergic reaction. Even if your pet only eats two small leaves, it can cause serious side effects so you should see a veterinary professional right away if your dog encountered a mayweed plant.

• Inflamed skin rash
• Pain and itchiness at the site of exposure
• Excessive drooling
• Appetite loss
• Depression
• Diarrhea
• Vomiting
• Weakness
• Nosebleed
• Allergic reactions (can be serious in some cases)
• Bleeding disorders (hemorrhaging, slow clotting)

 Types

The scientific name for mayweed is Anthemis cotula from the Asteraceae family. There are a few other names that the mayweed is known by, such as:

• Barnyard daisy
• Chigger weed
• Dog daisy
• Poison daisy
• Stinking chamomile

The toxic principles in mayweed are the volatile oils, which can cause reactions ranging from mild to lethal.

• Anthemic acid
• Bisabolol
• Chamazulene
• Tannic acid

Whether you witnessed your dog eating mayweed or not, you should be aware that it can be fatal if you do not get treatment right away. Therefore, it is safer for your pet if you make a trip to the veterinarian for a checkup. Your veterinarian will be able to tell you if your dog needs a more thorough evaluation after doing a physical examination. This will include your dog’s weight, body temperature, breathing rate, pulse, blood pressure, breath sounds, oxygen level, and reflexes. Afterward, a urine and stool sample may be taken for microscopic evaluation. 

If the veterinarian is still not sure, some blood will be drawn for laboratory testing. Some of these tests may include a chemistry profile to check the status of the liver and kidneys as well as the glucose and electrolyte levels. A complete blood count (CBC) will most likely be done to determine the levels of platelets, hemoglobin, hematocrit, red blood cells, and white blood cells. To check for dehydration, kidney and liver function, and shock, a packed cell volume (PCV) and blood urea nitrogen (BUN) will be performed. At this time, the veterinarian may also want to perform some x-rays or an ultrasound to look for obstructions and swelling as well as to see the sizes and health of the internal organs.

If the veterinarian decides your dog is suffering from mayweed poisoning, the treatment required will generally depend on the test results and your pet’s health. However, the most common treatment for this is evacuation, detoxification, medication, and observation.

Evacuation

To rid your pet’s body of mayweed toxins, the veterinarian will give a hydrogen peroxide solution or ipecac syrup. This will induce vomiting within 15 minutes or another dose can be given. After this, activated charcoal will be given by mouth to absorb the undigested toxins.

Detoxification

To detoxify your dog, a gastric lavage will probably be performed in which the veterinarian uses a tube to gently push warm, sterile water into the digestive system in order to wash away any leftover plant particles. Then, fluids will be given by intravenous (IV) line to flush the kidneys and rehydrate your pet.

Medication

If your dog has areas of contact dermatitis, a cortisone cream will be applied to ease the swelling and discomfort. Antiemetic medication may also be given to control the vomiting.

Observation

It is usually necessary to keep your dog in the hospital for observation so the veterinarian can give supportive treatments if necessary. IV fluids will probably be continued until your pet is allowed to go home.

Your dog’s prognosis is good if he received prompt treatment. The chances of recovery are lower if you delay taking your pet to see a veterinarian. It is imperative to go to your veterinarian or a veterinary hospital right away even if there are no visible signs of poisoning in your pet’s demeanor after the exposure or ingestion. You will need to keep your dog relatively calm for the next few days and he may need a bland diet as well.