Most poisonous fungi are distinguished from the non-poisonous by a warty cap. They are often viscid and have other peculiarities of structure, colour, etc. They are acrid or astringent, and have a pungent, disagreeable odour (Christison). Poisonous mushrooms may either produce violent gastro-intestinal symptoms, which are seldom fatal, owing to the prompt evacuation of the poison from the system, or these symptoms are followed by a condition of narcosis ending in fatal collapse. The pupils are contracted, the urine is suppressed, the face is livid, and there is general vasomotor paralysis. The conjunctivae are congested.

Muscarin is a substance isolated from poisonous fungi, which is a violent cardiac poison and constrictor of the pulmonary blood vessels, producing dyspnoea, prostration, and death. Its effects are antagonised by belladonna.