Tanya St.-Arnaud, 29, was attacked at her apartment in Longueil early Sunday in what police consider a domestic dispute with her boyfriend, police told the Canadian Broadcasting Corp.
Police spokesman Martin Simard told the broadcaster the woman was splashed on her face and upper body with an unidentified household cleaning product.
"We know that the product is very dangerous for the skin if it's not diluted," Simard said.
He said St.-Arnaud's life wasn't in danger and investigators would question her when doctors ease her out of the coma.
Soon after the attack, police arrested the woman's boyfriend, 27-year-old Nikolas Stefanatos and charged him with aggravated assault.
He is scheduled to appear in court Friday, the report said.