The rhus tree, a picturesque garden feature with red and orange leaves and small yellow berries, has brought at least nine people in Hamilton out in painful itchy blisters.
The tree, Toxicodendron succedaneum, is poisonous and, as residents of Leonard St in the suburb of Dinsdale arediscovering, contact with its leaves, sap, sawdust or even smoke from burning branches can cause severe allergic reactions.
Leonard St residents Jonathon Leet, 11, and his neighbour, Alison Bramley, 12, are the latest in their road to be affected by the tree, which was a popular ornamental plant several years ago and grows throughout the country.
Jonathon's mother, Natalie Leet, said it was the second time this year her son had developed nasty blisters, which were extremely itchy and weepy. This time the reaction was much more severe than the first.
Other residents in the street had also suffered from swollen faces, rashes and blisters, but no one knew what was causing the reaction.
One man was told by his doctor that he had shingles, and Jonathon was sent home from the doctor with antibiotics but no diagnosis.
The Waikato medical officer of health, Dell Hood, discussed the symptoms with the National Poisons Centre in Dunedin and diagnosed the blisters as a reaction to the rhus tree.
Dr Hood said it was important that people, especially keen gardeners, were aware of the tree and its effect, which could last several weeks.
"The rash we are talking about is not just inconvenient, it's very serious," Dr Hood said.
Each time a person was affected by the tree's poison, the symptoms would be worse. Some people had been admitted to intensive care.
A Waikato Hospital honorary associate professor, Marius Rademaker, said the reaction was known as phyton dermatitis and Waikato specialists saw up to 30 cases of it each year.
The number of people it affected seemed to increase during the autumn months and he had seen two cases this week.
People who come into contact with the tree, its leaves or berries should wash their hands with soapy water and seek medical help if blisters appear.
