An unseasonal rise in wild mushroom poisonings has caused the Royal Botanic Gardens and Domain Trust, together with NSW Health, to issue a warning against eating them.

Royal Botanic Gardens deputy executive director Dr Brett Summerell said recent wet and humid weather provided ideal growing conditions for wild mushrooms, including toxic varieties.

"Mushroom production is greatest usually between March and June when the weather starts to cool but this year the season has kicked in early because of these factors," Dr Summerell said.

"Those foraging and collecting wild mushrooms need to know that it's difficult to distinguish between edible and poisonous mushrooms.

"The best thing to do is avoid eating wild mushrooms.

"I must stress, that unless you're with an expert who knows each individual species of mushroom very, very well, you should not eat them, because many species are toxic and cause illnesses and in some cases, death."

NSW Health Protection and NSW Health director Dr Jeremy McAnulty, said there was concern about an increase in poisoning cases linked to eating wild mushrooms.

"In February, 10 people attended NSW hospital emergency departments with poisoning after eating wild mushrooms - eight more cases than is usually recorded for this time of the year," Dr McAnulty said.

"Four of the patients were recorded in Nepean Blue Mountains, two in Western Sydney, three in Central Coast and one in the Illawarra Shoalhaven."

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

Some varieties of mushrooms such as Death Cap mushrooms can cause death due to kidney and liver damage.

However, commercially available mushrooms are safe to eat.

The mushroom season is likely to continue for the next few months.

If you experience any symptoms following wild mushroom ingestion, please contact the NSW Poisons Information Centre on 13 11 26.

In an emergency, Call 000 for an ambulance or seek treatment through your doctor or emergency department of your nearest hospital.