A California woman was hospitalized after using a skin cream that was tainted with mercury and is now in a semi-comatose state.
"Sacramento County Public Health urges the community to immediately stop using similar skin creams imported from Mexico due to the risk of contamination with methylmercury," Dr. Olivia Kasirye, public health officer with the county's department of health, said in a statement. "Methylmercury is extremely dangerous to adults and children."
The cream in question, according to Sacramento health officials, is "used by consumers as a skin lightener and to remove spots and wrinkles."
The 47-year-old Latina woman who was exposed to the cream -- which was labeled as a Pond's product, but had been tainted with mercury -- presented with numbness and slurred speech that progressed to thrashing and non-responsiveness, which required that she be restrained to her bed, Dr. Lauren Kelly, who works for the ABC News medical unit explained.
"The mercury was not added by the Pond’s manufacturer, but by a third party after purchase," the health department said.
The cream she used was believed to be the cause of her symptoms after the California Department of Public Health laboratory analyzed it and found that it contained methylmercury iodide at 12,000 parts per million. It is illegal to sell skin cream products in the USA with 1 ppm or more of mercury.
Dr. Cyril Wecht, a forensic pathologist based in Pittsburgh, told ABC News that these levels of toxicity would develop "not immediately, but pretty quickly."
While signs and symptoms vary person to person, Wecht added that in this patient's case "It depends if she was using it every day and how long she was keeping it on."
Sacramento County Public Health said this is the first reported case of methylmercury poisoning of this type linked to a skin cream in the U.S., though multiple cases of mercury poisoning due to tainted skin-lightening creams purchased through informal networks and originating in Mexico have been described and detailed by the California Department of Public Health.
Mercury exposure can occur by including swallowing it, inhaling vapors and absorbing it from the skin; but the most common cause of toxic mercury exposure is by eating mercury-contaminated fish.
"With facial cream, exposure occurs by absorption after application to the skin, inhalation of the vapor and hand-to-mouth behavior leading to ingestion," Kelly explained. "The effects of an exposure depend on many factors including the form of mercury (i.e. organic or inorganic), the amount, the length of time exposed, the mechanism of the exposure and the age and health condition of the exposed person."
In terms of reversibility, Wecht said that depends on "how long the damage had been going on and how quickly it was recognized."
"From [a] neurological standpoint, it's hard to comment on reversibility of her symptoms," he said. "Effects of intoxication have a psychological component as well as a neurologic component. I have seen cases that have resulted in death."
The California Department of Public Health issued a health alert that outlines the full list of signs and symptoms, as well as the prolonged exposure and effects.
Ponds and Unilever, its parent company, did not immediately respond to ABC News' request for comment.