An investigation is being made into products used in a hair-straightening trend which is sweeping the world because of fears they contain dangerous levels of the cancer-causing chemical formaldehyde.

The Cosmetic, Toiletry and Fragrance Association of New Zealand (CTFA) has issued a warning to hairdressers, saying some products on the market are believed to contain between 10 and 75 times the legal level of formaldehyde.

Formaldehyde, which has also been linked to miscarriages, is found in nail polish and glues and is used in the funeral industry for embalming.

The hair-straightening promises shiny, smooth hair for up to four months at a cost of about $600.

Countries that have banned or issued removal notices on some of the products include the United States, Canada, Ireland.

Australia, which has the same formaldehyde thresholds as New Zealand, has also removed some products from the market but no withdrawal has been issued here because tests are still being conducted.

The hairdressing industry's concerns are about the inhalation of fumes from the formaldehyde which poses risks to hairdressers and their clients.

There are several hair-straightening products, all claiming to produce similar results.

They include Coppola, Brazilian - both of which have been removed from sale in Australia - and KeraStraight solutions.

The Department of Labour has confirmed it is testing the products on sale in New Zealand to check their formaldehyde levels, which must be below .02 per cent.

Results from the investigation are expected to be known within about three weeks.

But there are further concerns about people buying and selling products on the internet.

Environmental Risk Management Authority hazardous substances compliance manager Dr Simon Buckland said a complaint was referred to the Department of Labour, which is investigating because of the potential risk to staff and clients in a workplace environment.

All cosmetic products were meant to comply with regulations set by the Cosmetic Products Group Standard, he said.

CTFA executive director Garth Wyllie said no withdrawal had been issued in New Zealand because test results had not yet been released.

Most salons had sold out of the products and had not replaced them, which had gone some way to minimising risk.

He was not aware of injury or illness from use of the products.

Prosecutions against companies that sold products containing too much formaldehyde were occurring in Europe and the same could happen here, he said.

Angeline Thornley, general manager of the NZ Association of Registered Hairdressers, which represents 3800 hairdressers, said use of the products was an industry-wide concern.

However, distributors had acted responsibly after being made aware of the problem, she said.

Anyone concerned about non-compliance involving these products should contact the Department of Labour on 0800 209-020.