Between 2010 and 2012, there was a dispute between the manufacturers and importers of Brazilian hair straightening products on one hand, and various US federal and state health agencies on the other, about the proper labeling and health warning of the products. The dispute centered about the chemical compounds formaldehyde (H 2CO) and methylene glycol (H 2C(OH) 2), which are the active ingredients of the process, responsible for binding the keratin to the hair. Formaldehyde is a gas that, when dissolved in water (including fluids in the human body), converts partially to methylene glycol.