A 70-year-old woman has become the fourth person to be poisoned by toxic honey.

The Hamilton woman experienced symptoms of nausea and tremors and convulsions after eating comb honey on toast.

After suspecting her illness was due to a piece of carrot cake, she then realised it was the honey, which was bought while on holiday in Whangamata.

A Waikato District Health Board spokesperson says the honey, purchased from Meat at the Beach Butchers in Whangamata was also stocked at Valley Orchards and Quarry Orchards.

A drop-off point for honey bought from the three outlets has been set up at the Whangamata Medical Centre.

Earlier on Sunday, the last of three other suspected victims of toxic honey poisoning, English tourist Joseph Reynolds, left Thames Hospital.

A child and his mother were also admitted to hospital after eating the honey.

Toxic honey is produced when bees feed on honeydew on tutu bushes. Further to the nausea, symptoms include delirium, giddiness, increased excitability, stupor, coma and violent convulsions, usually developing within three hours of consumption.

As little as one teaspoon of toxic honey can have a severe effect on the human nervous system.