Deadly
Orellanine poisoning
Orellanine
Onset after the meal
2 days to 3 weeks
Later than six hours, which is the line that matters. A delayed onset means an organ is already being attacked, and it is an emergency even if the person feels well by the time they are seen.
Attacks
The kidneys
What it does
Nothing at all for days. Then thirst, heavy urination, then falling urine output, nausea, loin pain and the signs of kidney failure.
How it runs
By the time symptoms appear the damage is done. Serious cases end in permanent dialysis or a kidney transplant.
Treatment
Hospital and renal support. There is no antidote, and the window in which anything preventive could have been done has closed long before anyone feels ill.
The catch
The longest delay in mycology by a wide margin, and it means the meal is almost never connected to the illness. Anyone with unexplained kidney failure who forages should tell their doctor so, even about a meal a fortnight old.
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.