This proposed rule would ban formaldehyde (FA) and other FA-releasing chemicals (e.g., methylene glycol) as an ingredient in hair smoothing or hair straightening products marketed in the United States. These chemicals are used in certain cosmetic products that are applied to human hair as part of a combination of chemical and heating tool treatment intended to smooth or straighten the hair. Use of hair smoothing products containing FA and FA-releasing chemicals is linked to short-term adverse health effects, such as sensitization reactions and breathing problems, and long-term adverse health effects, including an increased risk of certain cancers. As hair smoothing products increased in popularity in the late 2000’s, FDA began receiving inquiries from consumers and salon professionals about the safety of products containing formaldehyde or related ingredients. In response to these concerns, in 2010, the Agency began communicating with the public to provide information about the potential health effects of these products and how to recognize products containing formaldehyde or its liquid forms. Since then, FDA has engaged in additional public outreach, including a series of focus groups with salon owners, salon stylists, and salon customers.  In 2021, FDA received a citizen petition from the Environmental Working Group and Women’s Voices for the Earth requesting that FDA take regulatory action to ban formaldehyde, formaldehyde equivalents, and other chemicals that emit high levels of formaldehyde in hair smoothing products and hair straightening products.