Although potentially fatal if eaten raw (causing restrictions on its sales in some areas), G. esculenta is still commonly parboiled for consumption, being a popular delicacy in Europe and the upper Great Lakes region of North America; evidence suggests that thorough cooking does not eliminate all traces of mycotoxins.

When consumed, the principal active mycotoxin, gyromitrin, is hydrolyzed into the toxic compound monomethylhydrazine, which affects the liver, central nervous system, and sometimes the kidneys.

The grouping includes other species of the genus Gyromitra, such as G. infula (elfin saddle), G. caroliniana and G. gigas (snow morel).

While some of these species contain little to no gyromitrin, many guidebooks recommend treating them all as poisonous, since their similar appearance and significant intraspecific variation can make reliable identification difficult.

The cap colour may be various shades of reddish-, chestnut-, purplish-, bay-, dark or sometimes golden-brown; it darkens to black in age.

[19] Enthusiasts in Finland have been reported burying newspaper inoculated with the fungus in the ground in autumn and returning the following spring to collect mushrooms.

[23] Although more abundant in montane and northern coniferous woodlands such as the Sierra Nevada and the Cascade Range in northwestern North America, Gyromitra esculenta is found widely across the continent,[7] as far south as Mexico.

Experts speculated the reaction was more of an allergic one specific to the consumer, or a misidentification, rather than innate toxicity of the fungus, due to the wide range in effects seen.

[32] Gyromitra poisonings are rare in Spain, due to the widespread practice of drying the mushrooms before preparation and consumption,[33] but has a mortality rate of about 25%[clarification needed].

[35] Evidence suggests that children are more severely affected; it is unclear whether this is due to a larger weight consumed per body mass ratio or to differences in enzyme and metabolic activity.

This reduces production of the neurotransmitter GABA via decreased activity of glutamic acid decarboxylase,[42] producing the neurological symptoms.

[35] Inhibition of diamine oxidase (histaminase) elevates histamine levels resulting in headaches, nausea, vomiting, and abdominal pain.

Additionally intravascular hemolysis causes destruction of red blood cells resulting in increase in free hemoglobin and hemoglobinuria which can lead to renal toxicity or kidney failure.

This is where higher than normal levels of methemoglobin, which is a form of hemoglobin that can not carry oxygen, are found in the blood.

[52] Treatment is mainly supportive; gastric decontamination with activated charcoal may be beneficial if medical attention is sought within a few hours of consumption.

[31] Monitoring of biochemical parameters such as methemoglobin levels, electrolytes, liver and kidney function, urinalysis, and complete blood count is undertaken and any abnormalities are corrected.

[54] Pyridoxine, also known as vitamin B6, can be used to counteract the inhibition by MMH on the pyridoxine-dependent step in the synthesis of the neurotransmitter GABA.

[58] Similar ALS clusters possibly related to mushrooms are found near the Aosta Valley (Italy), in Sardinia, and in Michigan.

Although Gyromitra esculenta has not been observed to cause cancer in humans,[64] it is possible there is a carcinogenic risk for people who ingest these types of mushrooms.

[66] Despite its recognized toxicity, Gyromitra esculenta is marketed and consumed in several countries or states in Europe and North America.

[20][64] Similarly in Sweden, the Swedish National Food Administration warns that it is not fit for human consumption,[67] and restricts purchase of fresh mushrooms to restaurants alone.

[69] In some countries such as Spain, especially in the eastern Pyrenees, they are traditionally considered a delicacy, and many people report consuming them for many years with no ill effects.

[75] In 2002, the Finnish Food Safety Authority estimated annual consumption of false morels to be hundreds of tonnes in plentiful years.

[76] In Finnish cuisine, false morels may be cooked in an omelette, or gently sautéed in butter in a saucepan, flour and milk added to make a béchamel sauce, or pie filling.

[79] In 2015, Swedish chef Paul Svensson [sv] caused a controversy when he prepared a dish with Gyromitra esculenta in a TV show.

Mushroom expert Monica Svensson criticized him for including it, because monomethylhydrazine is a known carcinogen and there is a risk that inexperienced people might misinterpret the recipe and omit the steps that reduce the toxicity level.

[38] If boiling the mushrooms indoors, care should be taken to ensure adequate ventilation, and, if symptoms of monomethylhydrazine poisoning appear, immediately open all windows and move outside to seek fresh air.