Are Wild Mushrooms Toxic to Pets?

Veterinary Insight for Pet Owners

Identifying Toxic Mushrooms

How poisonous are the mushrooms that your dog can find while wandering about outside? The answer is not a simple one. Whereas most mushrooms may cause mild, self-limiting nausea and diarrhea, they can look just like mushrooms that can cause life-threatening effects.

For example, morels are considered to be a delicacy to chefs and mushroom aficionados, but the false morel can cause significant vomiting, abdominal pain, diarrhea, and tremors.

Identifying a mushroom takes skill and expertise to evaluate the spore impressions, gills and fine hairs on the surface of the mushroom. Most people would not be able to appreciate the nuances that differentiate one mushroom from another. A mycologist, scientist who studies mushrooms, is needed to reliably identify a mushroom of concern. 

Mushroom Toxicity Symptoms

Although most mushrooms cause little beyond stomach upset, don’t assume that any mushroom is harmless.

When one of the more toxic wild mushrooms is ingested, there can be risk  for kidney and liver failure, protracted vomiting and dehydration. Some wild mushrooms can even cause hallucinations, Signs of more severe mushroom toxicity include profuse or bloody vomiting and diarrhea, excessive drooling and watery eyes, a slow heartbeat, depression, lethargy, abdominal pain, yellowing of the eyes (jaundice), and seizures.

Poisonous mushrooms can be classified into 4 groups based on the signs that can develop:

1. Gastrointestinal – vomiting, diarrhea, and abdominal pain can occur within 15 minutes to 2 hours after ingesting even a small amount. Signs often resolve on their own, but dehydration may need to be treated.

2. Liver and kidney – the most harmful type of mushrooms can be found throughout North America, especially from California to British Columbia and from Maine to Maryland. These mushrooms are generally found in association with trees.

Signs start with vomiting and diarrhea within 6 to 24 hours and can turn bloody. Liver and kidney damage occur after 24+ hours.

3. Central nervous system –

a. hallucinogenic mushrooms more commonly grow in fields and pastures in the northwest and southeast United States. Signs can occur within 15 minutes to 2 hours and may take 4 to 48 hours to recover.

b. false morels are found in Spring throughout North America often close to or under conifers and aspen. Vomiting and diarrhea start within 6-12 hours then lead to tremors and seizures.

c. some grow in the Summer and Fall in both deciduous and coniferous forests and are especially common in Pacific Northwest. These can cause seizures or similar signs withing 15 minutes to 2 hours.

4. Muscarinic - salivation, tearing (lacrimation), urination, defecation (often diarrhea), abdominal pain, and vomiting all occur together within 15 minutes to 2 hours. Some of these mushrooms grow under or around conifers or broad-leafed trees and others grow in grasslands or on the forest floor.

Treatment for Mushroom Toxicity in Pets

Treatment for mushroom toxicity is mainly symptomatic and directed at stabilizing the patient, removing or neutralizing the source of toxicity and treating clinical signs that develop.

Typical treatment includes inducing vomiting to decontaminate your pet’s stomach. Activated charcoal may then be used to adsorb any remaining toxins if the vomiting does not produce the entire ingested mushroom. If your pet begins to show signs of toxicity, it may be useful to try to identify the mushroom and the specific toxin ingested. If your dog has eaten a mushroom, try to take detailed digital photographs of the mushroom. Use a ruler or common item to help see the size of the mushroom. Try to get accurate colors and get a photo from the top, bottom, and sides of the mushroom. Take multiple samples as there may be several types of mushroom in one area. Know the location and substrate from where the mushroom was growing.

Mushroom samples should be wrapped in a paper towel then put them in a paper bag in the refrigerator in order to preserve them for examination. Label the bag “Do not eat!” Once at the veterinarian’s, the gills of the mushroom can be pressed onto a glass slide to take photos of the spores.

Mycologists can be found at universities and sometimes at botanical gardens.  Local greenhouses and extension offices may also be able to help identify the mushroom, as they are often familiar with common mushrooms in your specific area.

Identifying the mushroom is the best way to tailor tests and treatments as well as to predict outcome.

The best form of prevention is to keep your pets away from wild mushrooms and remove any that you discover growing in your yard or along your usual walking route. Should you suspect your pet has eaten anything toxic, contact your family veterinarian or Pet Poison Helpline immediately at 800-213-6680 or petpoisonhelpline.com.

Are peanuts safe for dogs? What about avocados? Read more about toxic substances to pets like onions, garlic, chocolate, nuts and xylitol.