Ten people have been admitted to hospital this month after eating wild mushrooms in various parts of New South Wales, prompting a warning from health authorities.

A recent bout of wet and humid weather has provided ideal growing conditions for wild mushrooms, including poisonous types, earlier than the usual start of the season in mid-March.

Four of the patients treated in hospital were from the Blue Mountains, two from western Sydney, three from the central coast and one in the Illawarra region.

Eating poisonous mushrooms can cause abdominal pains, nausea, vomiting and diarrhoea.

"In some cases the onset of symptoms could be quite rapid and if you're getting symptoms ... then it's important to go to the emergency department and get it checked out," fungi expert and Royal Botanic Gardens deputy executive director Brett Summerell said.

Two years ago, two Chinese tourists died after eating death cap mushroom in their meal in Canberra.

Dr Summerell said it was important foreign tourists were aware of the dangers of eating wild mushrooms in Australia.

"While they may be comfortable picking mushrooms in their home country, our species can be quite different and the consequences of eating them can be quite drastic," he said.

Dr Jeremy McAnulty from NSW Health said cooking poisonous mushrooms would not get rid of their toxins.

He said different mushrooms would cause different symptoms.

"We're concerned there's an increase in cases, unexpected for this time of year, entering into the season when wild mushrooms are more common, when people might be foraging," he said.

"Don't eat wild mushrooms, don't cook them or prepare them or get them yourself because you're running a risk."

Dr McAnulty said most of the people who foraged for wild mushrooms were looking for a meal rather than a high.

"It does seem sometimes people are after magic mushrooms and some hallucinogenic effects of those," he said.

"But it seems as though people are foraging to eat mushrooms they find in the wild and cook them for the benefit of food."

The mushroom season is expected to continue over the next few months.