The quick answer: It depends. Mushrooms from the grocery store that are meant for human consumption are not toxic to dogs, but wild mushrooms can be poisonous or deadly.
Benefits of mushrooms
If your dog is quick to clean up dropped food scraps, then you can rest easy knowing that edible mushrooms are safe for dogs to eat.
Mushrooms that are sold at the grocery store as food are low in calories and fat and contain copper, potassium, magnesium, and zinc. Mushrooms are also high in antioxidants and some mushrooms are a good source of vitamin D. Though your dog doesn’t need mushrooms in his diet to meet his nutritional needs, it is safe for him to try a bite or gobble up an accidentally dropped scrap.
Even edible mushrooms should only be consumed in moderation because too much of any type of food can cause tummy troubles. The total amount of fruits and vegetables (and fungi in this case) your dog consumes should make up no more than 10-20% of his diet.
All mushrooms growing in the wild are off limits and your dog should not be allowed to eat them. Depending on the type of mushroom, even just a small bite can cause poisoning. The most dangerous type of mushroom can cause liver failure and even death.
According to Pet Health Network, “there are thousands of mushrooms out there, but only about 100 types are poisonous.” However, it can be difficult to distinguish which wild mushrooms are toxic, so veterinarians recommend treating all wild mushrooms as toxic. This means seeking immediate veterinary care if you suspect your dog has eaten a wild growing mushroom.
Symptoms of mushroom poisoning will vary depending on the variety your pup consumed, but may include: