Muscarine Poisoning

Every year hundreds of people suffer from mushroom poisoning.  If the symptoms are experienced within a few hours of ingesting the mushrooms, we are not too concerned about the possibility of a premature demise.    The expectation from rapid symptoms is that you have ingested an alimentary toxin and that, after a few unpleasant hours or rarely days, you will make a 100% recovery with no lasting ill effects or damage to the vital organs (liver, kidney etc).

This is not always true, however, and some of the so-called non lethal toxins can occasionally cause death.  Again, however, this is often explained away on the basis that the person had some other debilitating disease and was weakened to the point where the mushroom toxin was the final straw.


Muscarine is one of those toxins that is not usually regarded as ‘deadly’.  It was first discovered in Amanita muscaria, hence the name.  The toxin is at very low levels in A. muscaria which contains several other toxins including the hallucinogenic compounds muscimole and ibotenic acid.   So, muscarine poisoning is not usually associated with Amanita muscaria.   Muscarine, however,  is known to occur at much higher levels in other mushrooms and is particularly high in a number of species of the genus Inocybe.   Muscarine concentrations in Inocybe are 100 X as high as they are in Amanita muscaria.

Inocybe falls into the category of Little Brown Mushrooms (LBMs).   In the common field guides, mushroom hunters are warned   repeatedly against gathering or eating LBMs.   Inocybe species vary from straw-coloured  to brown (click here) or dark brown  (click here) and some are lilac to purple (click here).  They are radially streaked, fibrous and often split at the margins (click here).  The common name for Inocybe is "Fibre Cap".   Inocybe species may also be smooth to hairy or even scaly and toughish.  They are not the kind of mushroom that afficionados normally seek out as a food source so muscarine poisoning of people is not that common.     Unless, perhaps, the mushroom hunters were foolish enough to mistake an Inocybe for one of the hallucinogenic Psilocybe species (magic mushrooms).    In Inocybe species the gills are attached to the stalk  and  maybe be whitish when very young but the spores are brown and the gills turn brown as they age.  

Inocybe species grow in association with trees;   as a rule, therefore, you are not going to find them on your lawn.  Of course, if you have carved your property out of a woodland wilderness,  Inocybe species may fruit where the grass meets the trees at the edge of the forest.   Inocybe species also tend to be a little tougher than your average mushroom.   Some of the more delicate mushrooms may dry up and disappear in a day or so.    The hardier Inocybe species tend to tough it out for long periods. Another important point is that Inocybe species often fruit on hard-packed soil or gravel and I have often seen it fruiting in abundance (hundreds) on gravel parking lots or adjacent to campsites in provincial and state parks.

The symptoms of muscarine poisoning are almost classic. There is a dramatic increase in salivation, lacrimation and perspiration accompanied by vomiting, diarrhoea, and stomach pains.  Death rarely occurs with this type of poisoning but has been recorded. The antidote for muscarine poisoning is atropine.    After treatment with atropine,  there is a rapid abatement of symptoms and a complete and permanent recovery.  On rare occasions muscarine poisoning can be fatal.

BUT WHAT ABOUT DOGS??????????????????

1. DESIRE - Dogs, especially pups, like to chew on things and are not always discriminating about what they swallow.

2. OPPORTUNITY - Inocybe species tend to be tough and persist for longer therefore the chances of encounter are increased.

3. DOSE - Dogs have a much smaller body weight than people. Therefore, they are getting a much larger dose. (Dose is related to body weight.    If a 10 lb puppy and a 200 lb man both ate one Inocybe mushroom then the puppy would be getting 20X the dose of the man.  Ah! There’s the rub!

4. RESULT - Your dog will show the symptoms outlined above of muscarine poisoning. Depending on the quantity eaten and the body weight of the pup then it is very possible that dogs might experience more severe symptoms than outlined above.  It is also possible that dogs are more sensitive to muscarine than are people although to be truthful I have no evidence to support this and the reverse could be equally true.

5. EVIDENCE -  Not much.  There are a number of anecdotal stories, however, that suggest that dogs, particularly small dogs, have suffered symptoms consistent with muscarine toxicity following ingestion of mushrooms.  In some cases treatment with atropine has resulted in immediate relief supporting the muscarine poisoning hypothesis. More important - dogs have died following symptoms consistent with muscarine toxicity.

6. BOTTOM LINE - Watch out for Inocybe species and protect toddlers and pets from ingesting these mushrooms.  The problem is that most dog lovers don’t know what Inocybe looks like.  So to help you out a bit I have included some pictures of a selection of Inocybe species.  Click on thumbnail for larger picture.

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  I have not put names on these as identifying Inocybe mushrooms to species is a formidable task.

Note: Inocybe is not the only mushroom that contains muscarine but is probably the most common and the most likely to be ingested by a dog.

For more information on edible and poisonous mushrooms see my book (click here)!

There is another common fungus that fruits around old stumps in lawns, parks, woods etc. called "Dead Man's Fingers" (Xylaria polymorpha).   Earlier this year I was sent a sample of this fungus by a concerned dog owner who said it caused severe symptoms in her puppy.   This fungus is hard and chewy and would be highly attractive to a teething pup.     The hard, black, fruitbodies last for several months and I would expect them to contain a number of  toxins or other unpleasant compounds to disuade those who would seek to consume the fruitbodies.