Health Canada has issued a list of 10 hair smoothing and straightening products it says contain higher-than-safe levels of the carcinogen formaldehyde.
The products, which are made by several different companies, are used in salons but aren't generally sold in stores.
The ministry is in the process of getting companies and distributors to remove the products from the market. If necessary, a spokesman said, the regulator could issue a stop-sale order and seize the products.
"Health Canada will do everything in its power to stop the sale of these products," said spokesman Stephane Shank.
Ottawa's probe into the products began with Brazilian Blowout solution, which the regulator said in October contained 42 times the acceptable level of formaldehyde.
In addition to Brazilian Blowout, the list of hair straighteners now believed unsafe includes three products by Marcia Teixeira, three by Global Keratin, one each by Coppola, IBS Beauty and Cadiveu, and Pro-Collagen RX Keratin Treatment.
Their formaldehyde levels ranged from 1.4 per cent to seven per cent, according to Health Canada's tests.
The substance is used as a preservative in cosmetics, but the regulator says it must be kept at levels of no more than 0.2 per cent. It said it had received 46 reports that people exposed to the hair straightening products were experiencing burning eyes, noses and throats, breathing difficulties and, in one case, hair loss. When inhaled frequently over a long period of time, the substance is also linked to cancer, it said.
The regulator advised consumers to stop using the products if they experienced any of the side-effects and urged stylists not to use them.
IBS Beauty said it was pulling its product from the Canadian market and writing letters to salons advising them to return unused quantities. The company said its own private tests showed the formaldehyde levels were lower than what Health Canada had reported.
"We have retracted our product and brought it out of Canada," said Daniel Kim.
The other companies could not immediately be reached for comment.