Deadly
Gyromitrin poisoning
Gyromitrin, hydrolysed in the body to monomethylhydrazine
Onset after the meal
5 to 12 hours
Inside six hours, which is the reassuring side of the line, with one qualification: a mixed wild meal can produce an early reaction that hides a late one.
Attacks
The liver, red blood cells and the nervous system
What it does
Bloating, nausea and vomiting, then severe headache, vertigo and exhaustion. In serious cases jaundice, destruction of red blood cells, seizures and coma.
How it runs
Most cases recover. Serious ones progress to liver failure, and fatalities are documented, particularly with repeated meals.
Treatment
Hospital. Pyridoxine, vitamin B6, is used for the neurological effects, which is unusual and specific enough to be worth naming to the clinician.
The catch
The toxin is volatile, so it partly boils off, which is why the tradition of parboiling exists and why the cook can be poisoned by the steam while the diners are fine. It is also cumulative in effect across meals, so a history of eating it safely means nothing.
Species that cause it
This is reference material, not clinical guidance and not a substitute for a poison centre. If somebody is unwell after eating a wild mushroom, call one now, tell them the interval between the meal and the first symptom, and keep an uncooked specimen.