Victoria's acting chief health officer Michael Ackland said recent rainfall over warm soil across the state had encouraged the growth of poisonous mushrooms, which could be mistaken for similar-looking edible ones.

"While commercially-sold mushrooms are safe, poisonings can occur when people gathering wild mushrooms inadvertently include toxic species," he said. "Anyone who becomes ill after eating mushrooms should seek urgent medical advice and, if possible, take samples of the whole mushroom for identification."

Professor Ackland said the most dangerous variety was the death cap, which is usually found near deciduous trees, especially around oak trees. It is a large mushroom, with a cap ranging from light olive green to greenish yellow in colour. The gills are white, and the base of the stem is surrounded by a cup-shaped sac.

"The death cap is extremely toxic and responsible for 90 per cent of all mushroom poisoning deaths. Death can follow within 48 hours," he said.

People who eat death caps often get violent stomach pains, nausea, vomiting and diarrhoea within six to 24 hours of ingestion. While these symptoms may subside after one or two days, doctors say this does not indicate recovery and that the person may still have serious liver damage that can kill them.

Professor Ackland said Amanita phalloides and the yellow staining mushroom, Agaricus xanthodermus, were also dangerous. He said the commonly found yellow staining mushroom turns yellow when the cap or stem is bruised by a thumbnail.

"These are often gathered and mixed with field mushrooms, and can cause nausea, abdominal pain and diarrhoea in some people... If you have any doubts about a species of fungus or mushroom, don't eat it," he said.

Dr Teresa Lebel, a Senior Mycologist at the Royal Botanic Gardens said the death cap was widespread across Melbourne in both public and private gardens. It is also found in regional areas.

"The death cap appears any time from January to June, but is most common a week or two after good rains in summer and early autumn," she said.

If you think you have eaten a poisonous mushroom, it is critical you seek medical attention immediately. Do not wait for symptoms to occur.

You can also contact the Victorian Poisons Information Centre for advice on 131126.