An Australian woman has been charged after allegedly lacing a colleague's curry with snail poison.

Police in the state of Western Australia say the alleged victim made a meal for her co-workers in February, which they shared at morning tea.

But when the 58-year-old returned to eat leftovers at lunch, she noticed bright green granules in the food and that her tongue felt numb after tasting it.

The accused - who was in a relationship with the alleged victim - has been charged with endangering the life, health or safety of another person after a months-long investigation, and will face court on 5 November.

Police allege the 43-year-old woman - who hasn't been named - visited a chemical storage shed before returning to the staffroom where the curry was kept.

After tasting it, the alleged victim handed the meal over to detectives, who identified the substance as snail pellets containing metaldehyde, a poisonous substance.

Commissioner Col Blanch told reporters the poison can cause serious injury or death.

"We're just very thankful that the person who tasted the curry was aware of something that wasn't quite right," he said, according to the Seven Network.