The FDA has taken action against one of the most popular hair-care treatments available, the Brazilian Blowout. This widely used hair-straightening procedure — in which a chemical solution is essentially burned into the hair to temporarily straighten it — involves a product that the FDA has deemed unsafe for both consumers and salon workers. The manufacturer of the Brazilian Blowout line of salon products — currently involved in a messy tangle of lawsuits — maintains that its product is completely safe. Here, a guide to this controversy:

What makes the Brazilian Blowout unsafe?
After a liquid product is applied to a customer's hair, the hair is heated with a blow dryer and then treated with a flat iron. But Brazilian Blowout contains a chemical, methylene glycol, that releases formaldehyde gas when it gets hot. The presence of formaldehyde is what the FDA finds objectionable.

What's unsafe about formaldehyde?
It's known to cause cancer. Earlier this year, the FDA listed formaldehyde as a carcinogen. It now says Brazilian Blowout contains up to 10 percent formaldehyde, "which puts it [on par with] embalming fluid used by funeral homes," says Sora Song at TIME, much higher than the 0.2 percent considered safe.

Has the Brazilian Blowout caused any problems?
Many. Users have reported nosebleeds, eye irritation, headaches, dizziness, vomiting, rashes, and breathing problems after getting their hair straightened with Brazilian Blowout. (In fact, salon workers and customers often wear gas masks during a Brazilian Blowout procedure.) Those complaints are at the center of the several lawsuits that Los Angeles-based manufacturer GIB is now facing. The products are already banned in Canada.

What does the company say about its products?
They're completely safe, according to GIB company spokesman Mike Brady. "Anytime anyone has a negative reaction to a beauty product, it's a shame," says Brady, as quoted by ABC News, though he insists Brazilian Blowout has passed "countless" government safety tests. The product's packaging even states that Brazilian Blowout is "formaldehyde free."

What will happen next?
The FDA has given GIB until mid-September to straighten things out with the agency, specifically by modifying its ingredient list to exclude any form of formaldehyde. Failure to do so could result in the seizure of Brazilian Blowout products, and legal proceedings against the company.

Sources: ABC News, FDA, TIME, WebMD