After regularly using a skin lightening cream manufactured in Mexico, a California woman was hospitalized, relying on tubal feeding and being unable to speak or care for herself.

The U.S. Centers for Disease Control and Prevention (CDC) has linked her severe central nervous system damage to organic mercury poisoning via methylmercury, an organic mercury compound that has not caused a case of poisoning in America in nearly 50 years.

Methylmercury poisoning has the potential to cause severe central nervous system damage. The woman first sought medical help for muscular weakness and involuntary muscle movement in her shoulders and arms.

Two weeks of outpatient care ensued, but her symptoms worsened: her vision became blurry, she developed difficulty speaking and her gait became unsteady. After blood and urine tests confirmed mercury poisoning, she underwent chelation therapy.

Chelation therapy treats heavy metal poisoning via chemicals administered through intravenous therapy, intended to bond with the ions of the metals within the bloodstream. Once bonded, the heavy metals can be safely excreted by the patient.

But the patient's condition worsened, and she was transferred into hospital care, where she remains.

The patient used the cream twice daily for seven years, according to her family and a case study published December 19 about her illness in the CDC's Morbidity and Mortality Weekly Report.

Skin Cream
A woman who used a Mexican brand of skin lightening cream twice daily for seven years has been hospitalized with central nervous system.ANNELEVEN/GETTY

"Most harmful skin-lightening creams are intentionally tainted with inorganic mercury. But in this case, the patient used a skin-lightening product containing organic mercury, which is far more toxic," study senior author Dr. Paul Blanc, of California Poison Control System and the University of California, San Francisco (UCSF) to the Associated Press.

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"Central nervous system toxicity, as in this case, is the hallmark of organic mercury—it typically comes on after weeks to months of exposure. Once manifested, it quickly progresses and often worsens, despite removal of any further exposure," Blanc continued in a news release released by UCSF related to the study. "Unfortunately, chelation therapy, which is effective in inorganic mercury poisoning, has not been established to be efficacious for methylmercury."

Consumers looking to protect themselves from harm may "purchase creams from well-known stores and avoid those with hand-made labels or without labels. Ingredients must be listed, and directions and warnings should be in English," Dr. Craig Smollin, the study's co-author and member of UCSF's emergency department, said. Smollin is also the medical director of the California Poison Control System's San Francisco Division.