Why is the death cap the deadliest mushroom, even when it tastes fine?

The death cap is the deadliest mushroom for three reasons: its poison is extremely powerful, it survives the kitchen, and it does its damage before anyone suspects. Amanita phalloides is deadly poisonous. It is estimated that as little as half a mushroom contains enough toxin to kill an adult, and it is responsible for 90 percent of mushroom-related deaths every year.

The poison is a family of amatoxins. The main one, alpha-amanitin, causes liver and kidney failure. It works by blocking an enzyme that cells need to make messenger RNA, so essential protein synthesis grinds to a halt and the cell dies. Amatoxins are also thermostable: cooking or freezing does not reduce their toxic effects.

The danger is made worse by how the death cap behaves. It has been reported to taste pleasant, and the symptoms are delayed, so organs are being badly damaged before anyone is worried. Early stomach symptoms can seem to fade after up to 24 hours, yet symptoms of liver and kidney damage start 3 to 6 days after the mushrooms were eaten. It also resembles several edible species, most notably Caesar's mushroom and the straw mushroom, which raises the risk of accidental poisoning. Its cap colour varies, so colour is not a reliable identifier. Eating it is a medical emergency requiring hospitalization.

History has a famous case. Holy Roman Emperor Charles VI fell ill after a dish of sautéed mushrooms in October 1740 and died 10 days later, with symptoms consistent with amatoxin poisoning. Voltaire noted that this mushroom dish changed the destiny of Europe.