RIO DE JANEIRO, Brazil - Erlice de Oliveira juggles two kids, a full-time job, a long commute -- and really resents the time it takes to tame her curly hair every morning.

She had heard of a hair-smoothing treatment that worked well but used potentially dangerous chemicals. Still, all her friends were talking about it and Hollywood celebrities endorsed it. She decided to check it out.

"It looks like I just walked out of the salon," the secretary said. "My life is rushed; I can't go to the salon all the time. This is easy and practical."

Known as the Brazilian Blowout in the United States, the treatment surfaced around 2005 in Brazil, where a combination of high humidity and a largely mixed-race, curly-haired population made for a nation of eager customers. It soon spread throughout North America and Europe.

Available in several brands, the process often contains varying levels of formaldehyde, which has been classified by the U.S. Environmental Protection Agency as a probable carcinogen. According to complaints, it has made some stylists cough and reddened the eyes of clients.

The flap has rattled the beauty world: Canadian authorities issued a warning about possible health hazards; France pulled products with high levels of formaldehyde; the Oregon occupational health agency tested 100 samples and found many labelled "formaldehyde-free" had more than the 0.1 per cent of the chemical allowed in U.S. products.

A later air sample test of salons in Oregon found levels of formaldehyde complied with safety standards. But Michael Wood, who heads the state's Occupational Safety and Health Administration, said in a statement: "It is clear that the levels are high enough to cause concern."

Repeated emails and phone calls to the Los Angeles office handling public relations for the Brazilian Blowout brand were not returned. In a November news release, the company underscored the air sample tests from Oregon that found "formaldehyde exposure levels safely below OSHA's Action Level."

The U.S. Food and Drug Administration is still investigating whether the ingredients cause health problems. The California attorney general, meantime, has filed a lawsuit alleging the Brazilian Blowout brand has high levels of formaldehyde despite claiming otherwise on its website and other advertising.

A separate class action lawsuit filed in California makes similar allegations of false advertising, although it includes no reports of illness.

"Our client filed suit because she felt that she and other consumers were mislead by claims that the Brazilian Blowout hair treatment was all natural and did not involve the use of formaldehyde or other harsh chemicals," said San Francisco attorney Daniel Girard. "We have been contacted by many consumers and salon workers who have expressed interest in the litigation."

After-hours with her stylist applying the products, blow-drying her hair, then flat-ironing it at about 230 C -- which creates clouds of acrid-smelling smoke that stings the eyes -- Oliveira remains a satisfied customer with a no-fuss mop of shiny black hair.

She has been preaching the benefits of the process to friends ever since, and had another treatment since the first in July.

The treatment was nothing short of a miracle for women with curly, kinky or hard-to-tame hair. After a lifetime of fighting frizz with endless sprays and creams, only to see their efforts vanish with a gust of wind, they could get a smooth, fresh-from-the-salon look that lasted for months.

Because of the health concerns, however, some U.S. salons have stopped offering the Brazilian Blowout. Upscale salons in Ipanema, the Rio beach-side neighbourhood that sets fashion trends in Brazil, have sworn off treatments that use formaldehyde.

Jussara Fernandes said she won't let anything with the chemical into her Ipanema salon, which instead offers four different types of hair-smoothing or straightening treatments with prices ranging up to $250.

She remembers as a child hearing her mother and other women mention formaldehyde as a potent straightener in home-brewed mixes. In her 14 years as a stylist, she's seen horrors from overuse of the chemical -- women with bald patches from negative reactions, or ulcers on their heads.

"I'm adamantly against it," she said. "I have clients who've been coming here for years -- I care about their health and the health of my professionals. But there are people who do it."

Many of the women who've grown addicted to their smooth locks continue to swear by the process -- and many salons in Brazil, the U.S. and Canada continue to offer versions of the treatment with reduced formaldehyde levels.

"The smell is still really strong -- you can't have children in the salon, and you have to have the fan on," said Oliveira, who works for a real estate agency.

But it's a small price to pay, she said, for the ability to wake up, shower and be out of the house in 15 minutes with perfect hair.

As long as stylists and clients are well-informed and take precautions, it's worth it, said Xavier Guerin, a business partner at the Point de Vue salon in West Hollywood, Calif. The salon does Brazilian Blowout treatments, though they're careful not to book several treatments in a day, and they keep the place well-ventilated.

"Time in our modern society is such an issue, and you need to be more and more perfect. There is all this pressure," he said. "My experience is that most of our clients are ready to pay the price."

When the straightening treatment started in Brazil, stylists mixed their own formulas in beakers with formaldehyde, water, keratin and other ingredients.

In 2009, the government agency in charge of health and safety, Anvisa, started cracking down on salons that overuse the chemical. In January alone, they investigated 202 salons suspected of spiking their products, according to a spokesman. The sale of formaldehyde in pharmacies and supermarkets was forbidden in 2009 to stop the practice.

The new products, with limited amounts of formaldehyde, don't straighten the hair as much or last as long, which leaves many stylists and their clients longing for the days when the product was unregulated.

"These new products, they just don't work as well -- you have to do it two, three, four times on some people for it to really work," said Ana Paula Santana, a Rio hairstylist. "If you're going charge someone $120 for something, it had better make a difference."

In spite of the prohibition on using higher doses of the chemical, it still goes on in back yards around town, said Felipe Peres, hairdresser at Prima Qualitta in downtown Rio. He hears of salons that close down at night and take in clients. He also sees women with brittle hair ruined by too much formaldehyde who come in desperate for a fix.

"We're not chemists, we're hairdressers," he said. "There are people who aren't even hairdressers who do this."