The incident has sparked a public health alert from the territory's chief health officer Kerryn Coleman, warning Canberrans not to pick or eat wild mushrooms.

As the name suggests, the poisonous death cap mushrooms can be lethal.

In non-lethal poisoning they can also cause nausea, vomiting and diarrhoea, with symptoms generally developing within six to 24 hours.

Death cap mushrooms grow in areas across the territory, often near established oak trees, though they can be found elsewhere.

Dr Coleman said the young child was admitted to hospital on Tuesday after eating one of the poisonous mushrooms that can be easily confused with edible mushrooms.

"All parts of the mushroom are poisonous whether they have been cooked or not," Dr Coleman said.

People should avoid touching them with their bare hands, let alone eating them.

Anyone who thinks they may have eaten one should seek urgent medical attention, even if they don't display symptoms, and if possible should take the mushroom with them for identification.

"The chances of survival increase when treatment is started early," Dr Coleman said.

People should only eat mushrooms they've bought from a reputable supplier and not risk eating mushrooms found in the wild.

The ACT government conducts weekly inspections at sites known to produce high yields of the mushrooms between February and June.

Public sightings can also be reported to Access Canberra on 13 22 81.

Australian Associated Press