Two women suffered facial burns linked to "permanent cosmetics" when they went for an MRI scan, prompting a call to clamp down on makeup tattoo inks.
Permanent cosmetics - a form of tattooing around the eyes and lips - are rapidly growing in popularity.
But the magnetic field produced by an MRI (magnetic resonance imaging) can induce an electric current in the ink if it contains iron oxide.
That can heat the skin, particularly in sensitive areas around the eyes and lips.
The two women were in an MRI for only seconds before they suffered severe pain around the eyes and lips and their scans had to be stopped. The skin was left temporarily red and swollen.
There was no permanent damage but the Auckland clinic, which did not want to be named, says the women will not be able to have MRIs in future. It reported the matter to the Health Ministry's Medsafe division, seeking greater controls on tattooing inks.
Royal Australian and New Zealand College of Radiologists spokesman Dr Quentin Reeves said he had seen only 10 such cases in his 30 years of practice.
"The risk of permanent damage is extremely low. Most times the burning or prickling sensations can be controlled with wet towels over the tattoo."
The problem was associated with iron-oxide in tattoo pigments. "If there are tattoo artists doing it with higher iron oxide they should be told not to."
Some patients can have a CT scan, but in some situations there is no alternative to MRI.
Reeves said MRI was better at imaging health conditions such as brain tumours, soft-tissue tumours and major joint injuries and did not expose patients to radiation.
A ministry spokeswoman said Medsafe was aware of the issue and was investigating to determine how best to ensure those potentially at risk of burns from these products were informed of the risk.
Auckland Council's environmental health manager, Mervyn Chetty, said there was nothing in its health bylaw and code, which covers commercial tattooing, to prevent use of dyes with iron oxide in relation to MRI risks.
But under the Government's Tattoo and Permanent Makeup Substances Group Standard, inks with hazardous properties were not approved.
The council would check compliance with the standard if it received specific complaints.
Permanent cosmetics technician and trainer Michelle O'Byrne said her business, Wake Up With Make Up, used pigments that were free of iron oxide.
"We would be happy to drive our industry to be regulated," she said.