Never eat a wild mushroom identified only from a website, a book or an app. Have every find checked in person by an expert, such as a mycological society.
Identification
Russula emetica is a medium-sized brittlegill with a bright scarlet to cherry-red cap, 3–10 cm across, convex then flattened or slightly depressed. The cap is shiny and sticky in wet weather, and the skin peels away almost to the centre, revealing pinkish-red flesh beneath. The gills are white to very pale cream and, like the white, rather fragile stem, snap cleanly rather than bending, a feature of the whole genus. The spore print is white.
The flesh is white and crumbly, with a faint fruity smell and an extremely hot, peppery taste. Russula is a very large genus with many red-capped species, and separating them reliably requires spore print colour, chemical reactions (for example with iron salts or guaiac) and microscopy of the spores and cap cuticle. In the strict sense, Russula emetica is defined by its habitat in wet conifer woods; the similar beechwood sickener (Russula nobilis, also called Russula mairei) grows with beech.
Habitat and ecology
The sickener is an ectomycorrhizal fungus associated mainly with conifers, particularly pine and spruce. It favours wet, acidic sites, including bog margins and mossy woodland with sphagnum, and fruits from summer to late autumn. It is widespread across Europe and other parts of the Northern Hemisphere, but many records under this name, especially from outside Europe, probably refer to other red Russula species.
Like other brittlegills, it is an important partner of forest trees, helping them to take up water and nutrients in poor soils.
Uses and importance
The sickener has no culinary use. Its scientific and educational value lies in identification training: it demonstrates how taste, habitat and microscopic features are used in the large and difficult genus Russula.
The compounds responsible for its effects have not been fully characterised. Its burning taste is thought to be due to sesquiterpenes, and the irritant substances act on the gastrointestinal tract. The species name and common name both refer to its ability to cause vomiting.
Russula species are also studied in ectomycorrhizal ecology because they make up a large part of the fungal community on the roots of many forest trees.
Safety and edibility
Do not eat the sickener. Eating it, especially raw or undercooked, causes gastrointestinal poisoning with nausea, vomiting, abdominal pain and diarrhoea, usually starting within a few hours. Most cases resolve, but fluid loss can be dangerous for children, older people and people with other illnesses.
Anyone who has eaten this mushroom, or an unidentified red mushroom, should seek emergency medical help immediately, even before symptoms, and keep the remains for identification.
Taste-testing is sometimes used by experts for Russula, but it must never be used as a substitute for identification and is dangerous with unknown mushrooms, since some deadly species occur among white-gilled fungi. Never rely on a website, app or photo; have every wild mushroom checked in person by an expert such as a mycological society or a trained mushroom adviser.
If you suspect mushroom poisoning, call your local emergency number or poison centre straight away, even before any symptoms appear, and keep the remains of the mushrooms.
Look-alikes
A fly agaric (Amanita muscaria) whose white warts have been washed off by rain can look similar from above, but it has a ring on the stem and a bulbous base with rings of volval remnants; always dig up the whole stem base. Among brittlegills, Russula nobilis grows under beech, Russula rosea has a mild taste and a pinkish stem, and the edible charcoal burner (Russula cyanoxantha) has a variable violet-green cap and flexible gills. Many other red Russula species can only be separated by experts using microscopy.
Around the world
The sickener is common in conifer forests and bog margins across Europe, including the British Isles, Scandinavia and the mountains of central and southern Europe. Red brittlegills with similar features occur worldwide, but many of them are now treated as separate species, so the name Russula emetica should be used with care outside Europe.
