On a Monday afternoon in the fall of 2010, Jennifer Arce went to her sister Gina Griffin's house near San Diego to try out a popular professional hair smoother called Brazilian Blowout Açai Professional Smoothing Solution. Most hair smoothers, treatments that get rid of frizz and leave hair smooth and silky, contain formaldehyde, which is noxious when inhaled. Brazilian Blowout was labeled formaldehyde-free.

Arce, who was 36 at the time, had just been certified by GIB, LLC, the company that produces Brazilian Blowout, to administer the treatment. Certification ensures that the stylist knows how the chemicals will react with hair. A hair stylist for almost 20 years, Arce had her first Brazilian Blowout client booked for the following Thursday, but wanted to try it on herself first.

Arce, who grew up in southern California and has blue eyes and blond, curly hair with brown streaks, knew she wanted to be a hair stylist since she was a child.

"I used to play with my Barbies. I had a little hair salon in my backyard," she says. She used to flat iron her own hair all the time. "I liked it smooth and straight."

At her sister's house, Griffin, then 42 and working in the same salon as Arce, combed the soupy, cream-colored solution into Arce's freshly washed, frizzy hair. Then she began to blow-dry it. So far so good. Next, she would flat iron it, then rinse, and then a final blow dry.

Before the heat settled in, Arce's eyes began to tear up and scorch. She felt a pain that quickly became shockingly intense, as if someone had shoved an onion in her face and magnified the sting a million times. Her lungs felt aflame. Her sister couldn't breathe either. The chemicals were still in her hair, though, so there was no choice but to continue the rinsing process.

(More from Narratively: Crooked lines)

Days after her first exposure to Brazilian Blowout, Arce continued to have difficulty breathing and sought medical help. Her doctor, who had never previously heard any complaints about Brazilian Blowout, said she might have chemical poisoning and prescribed an inhaler.

Turning to the internet, Arce found a product warning on the website of Oregon Health and Science University. A Portland-area salon had alerted OHSU's toxicology center about Brazilian Blowout several months earlier. The salon's workers had suffered symptoms similar to those Arce experienced. OSHU researchers found that Brazilian Blowout contained a significant amount of formaldehyde. A chemical found in embalming fluid, formaldehyde is listed as a possible cause of cancer by the U.S. Department of Health and Human Services.

(Narratively/Jackie Snow)

But last year, readers of American Salon magazine, the premier publication for beauty professionals, voted Brazilian Blowout the Best Professional Smoothing Treatment for the third year in a row. A visit to the product's website shows beautiful models with straight, shiny locks. Bold letters on their "About" page tout the product as "the most innovative and effective in the world."

Hair smoothers like Brazilian Blowout work by forming a protective protein barrier around the hair that leaves it easier to straighten and lasts for an average of three to four months. Most hair smoothers — including popular brands like Keratin Complex by Coppola, Marcia Teixeira and Brazilian Silk — contain keratin, a key protein found naturally in hair, nails and skin. Brazilian Blowout, however, is amino acid-based.

What both types of smoothers have in common is their use of formaldehyde, which is essential to the hair smoothing process. "The more formaldehyde there is," says Eric Eulia, manager of Le Salon East in Manhattan, "the more it will last on your hair."

That Monday afternoon was the first and last time Arce tried Brazilian Blowout. For weeks after that first treatment, Arce got sick every time she applied heat to her hair. She tried to wash the product out. That didn't work. She sometimes had to leave her house with her hair wet because she couldn't bear what happened when she straightened it. She was, however, very satisfied with the way her hair looked when it was finished that Monday. It was smooth and sleek.

"I loved it," she says.

(More from Narratively: The hair down there)

Arce was not the first in her salon to raise concerns about Brazilian Blowout. When she first experienced symptoms, she says some of her co-workers also reported raw, sore throats and were put on antibiotics after providing the treatment to their customers.

Hoping to eliminate the problem, Arce and her co-workers brought the research they'd found to the salon's owner. They wanted Brazilian Blowout banned from the salon. Arce says the owner banned all hair smoothing treatments, including Brazilian Blowout, without hesitation. Halting the in-demand treatments might have been a difficult decision, since they range from $200 to $500 per client.

Time passed, and Arce slowly started to feel healthy again. But one Tuesday about two months later, she came to work and noticed she was having trouble breathing. Again, she wasn't alone. Her sister Gina began to get nosebleeds.

The salon, which serves a diverse clientele — white, black, young, and old — seemed to have formaldehyde residue in the air from a hair smoothing treatment done three days earlier. Arce says the owner had allowed it to be done when she wasn't working.

"It was kind of done behind our back," says Arce.

Feeling betrayed by the salon's owner, the two sisters quit and found work at a different salon. When hired, Arce showed the new owner OSHU's research.

Arce says her new boss also immediately banned Brazilian Blowout, but that some of her new co-workers traveled to their clients' homes to apply it there. Brazilian Blowout residue remains in the hair for weeks, so when those same clients came back for another wash, the heat from the blow dryer released the formaldehyde. (Arce felt uncomfortable revealing the names of the employers and co-workers she says continued to use Brazilian Blowout. "I don't want to hurt their business in any way," she says.)

Arce continued to get sicker, occasionally breaking out in rashes and coughing up blood. Trips to the doctor, covered by insurance through her husband's job, became almost as routine as trips to the salon. She was now using two different inhalers. "If I get exposed, in order to even breathe I have to use the inhalers," says Arce, who wouldn't consider changing careers, despite her persistent ailments. "This is all I know how to do," she says.

(More from Narratively: Living with lupus)

Brazilian Blowout first appeared on the market almost six years ago, at the Argyle Salon & Spa in West Hollywood, California. Scores of publications, from The Washington Post to Shape magazine, reported that it was all the rave among celebrities like Jennifer Aniston and Halle Berry.

But after studies revealed that Brazilian Blowout was potentially hazardous, it was banned in several countries, including France, Germany, Ireland, and Canada. In November 2010, the California attorney general filed a suit against Brazilian Blowout's company, which is headquartered in the state, claiming they had been deceitful about the products' dangerous chemicals. The FDA wrote a letter to the company's CEO, Michael Brady, requesting that he fix the misleading labels. That didn't happen. Last year Brazilian Blowout settled the lawsuit and paid a $600,000 fine as punishment. The agreement dictated that the company could continue to legally sell Brazilian Blowout, but only as long as it warns consumers about the formaldehyde in it. The company complied, and also settled a class-action lawsuit for almost $4.5 million.

(Narratively/Jackie Snow)

The settlement with the California attorney general required that the Brazilian Blowout formula be tested to see if it violates California's air quality law. Three bottles of the smoothing treatment were tested at three separate locations. The result found that the product's fumes violated California's Volatile Organic Compounds limits, which if exceeded can be a danger to human health.

The company issued a press release in November 2012, announcing it was moving production from Brazil to California. Although it still contains formaldehyde, the company said the U.S. version will meet California's air quality standards.

"The only difference stylists will notice," Brady said in the press release, "is a new sticker on the bottle which proudly reads 'Made in the USA.'"

The company also introduced a new product, Brazilian Blowout ZERO+, which is completely formaldehyde free. "However, the results of the Zero products are not as good," said Alonso Salguero, owner of Salon Ziba in Manhattan.

Brady told The New York Times that the class action lawsuit fine would be paid by his insurance company and stressed that Brazilian Blowout is harmless when used in a ventilated area. "We just want people to treat it like they do aspirin — make sure you only use it as directed," Brady said. (Representatives of the Brazilian Blowout brand did not return a request for comment on this article.)

Brazilian Blowout is not the only cosmetic product that has reportedly caused irreparable bodily damage. Stillman's Skin Bleach Cream was found to contain mercury, yet is still sold all over the world. Radithor, a mixture of radium and water meant to increase a man's sex drive, also ran into problems and is no longer marketed. In 2012, a lawsuit was filed against Unilever, claiming that formaldehyde was present in the company's Suave Professionals Keratin Infusion 30 Day Smoothing Kit. One woman, Tonja Millet, told Texas-based WFAA News that the Suave product "melted" her hair. She was told by the product's consumer hotline that she most likely didn't use it correctly. Unilever voluntarily recalled the product from stores in May 2012.

Read the rest of this story at Narratively.

Narratively is an online magazine devoted to original, in-depth and untold stories. Each week, Narratively explores a different theme and publishes just one story a day. It was one of TIME's 50 Best Websites of 2013.