Deadly webcapCortinarius rubellus

The deadly webcap (Cortinarius rubellus) is one of the most dangerous mushrooms in Europe. It contains orellanine, a toxin that destroys the kidneys. It's a medium-sized, fox-orange mushroom, often with a small pointed bump in the middle of the cap, rusty gills and yellow bands on the stem. Two things make it so dangerous: it grows right among trumpet chanterelles, so it ends up in baskets, and the first symptoms appear days after the meal, when the kidneys are already damaged.

Where does it grow? Mainly in conifer and mixed woods with spruce or pine, sometimes fir, and occasionally elsewhere, on wet, acidic ground among moss, sphagnum and bilberry. It appears singly or in small groups from summer to late autumn, mostly in late summer and early autumn. It's far more common in Scandinavia.

Deadly webcap or chanterelle? Chanterelles and trumpet chanterelles have no true gills: underneath they have thick, blunt, forked ridges running down the stem, and the trumpet chanterelle has a hollow stem. The deadly webcap has thin, blade-like gills, ochre when young and rusty brown later, covered by a cobweb-like veil in young specimens, and a stem with yellow bands. Its spore print is rusty brown. Pick trumpet chanterelles one at a time, never by the handful, and if anything with true gills turns up in your basket, the safest thing is to throw the whole lot away. Telling it from a cep is even easier: ceps have a sponge of pores under the cap, never gills. Yet that's the very mistake behind the Nicholas Evans case below, so always check for gills.

What are the symptoms? Orellanine attacks the kidneys. The first signs, which include nausea, vomiting, stomach pain, an intense thirst, headache and aching muscles, usually come one and a half to six days after the meal, occasionally as soon as the next day, and kidney failure can develop as late as two to three weeks afterwards. By then the kidneys are already damaged, and people often don't connect the illness with mushrooms at all. The damage is often permanent: in Sweden, 9 of 22 poisoned people were left with kidney failure, and five of them had transplants. There's no antidote. Cooking, frying and drying don't destroy the toxin, and dried mushrooms stay poisonous for decades. If you or anyone else may have eaten one, call emergency services on 112 (999 in the UK) or your local poison centre straight away, even if you feel fine. Tell the doctors that symptoms can be delayed by days, and keep any leftovers or photos.

The species was described in 1887 from Orton Moss near Carlisle, yet its danger was only recognised in 1972, in Finland. The first British cases followed in 1979, when three young people on holiday in Scotland mistook it for chanterelles, and two of them later had kidney transplants. The best-known case is that of Nicholas Evans, author of The Horse Whisperer. In 2008 he picked mushrooms in Scotland that he thought were ceps. Four adults were poisoned and all needed dialysis, and Evans later received a kidney from his daughter. Orellanine itself is now being studied as a possible treatment for one type of kidney cancer, precisely because it targets kidney cells so selectively.

Its close relative the fool's webcap carries the same toxin. It grows mainly in broadleaved woods and usually lacks the yellow stem bands, but for safety the difference doesn't matter, as both are deadly. People looking for magic mushrooms have also mistaken it for a liberty cap because of its pointed cap, and in Austria that ended in kidney failure. That's why most experts advise against eating any orange or brown webcap at all.