SAN FRANCISCO (AP) — California health officials became alarmed when a 39-year-old Mexican-American woman in Alameda County was diagnosed with mercury poisoning, giving her headaches, numbness, depression and forgetfulness.

Scouring her home for the likely culprit, they determined that an illegal skin-lightening cream smuggled in from Mexico was to blame.

Health investigators are currently going undercover in some San Francisco Bay Area ethnic communities to root out the foreign-made products whose pigment-busting ingredient can have damaging side effects.

The unlabeled jars of mercury-laced cream are typically used to lighten skin, fade freckles and age spots, as well as treat acne.

The investigators are working with health and beauty workers in the immigrant communities of San Francisco, Oakland and San Jose to hunt for the skin creams in shops and at swap meets, while encouraging families to dispose of the products safely.

The California Department of Public Health sent out a medical alert to health care professionals earlier this month, calling on them to notify the state of potential mercury poisoning cases and to ask their patients to stop using their creams.

California health officials worked with the Centers for Disease Control and Prevention to write a report in January that indicated at least 22 people in five households in California and Virginia had shared skin-lightening creams made in Mexico. Twelve people in California and 10 in Virginia had mercury in their bloodstream; the highest levels were among women who typically used the cream at least twice a day.

Officials would not release the names of the people in the study that began in 2010, saying they wanted to protect their privacy. After the study began, samples of the cream tested in Virginia showed that it contained 5 to 6 percent mercury, according to state health officials there.

The Minnesota Department of Health warned residents last year that skin lightening products being sold in African, Asian, Latino and Middle Eastern communities in the Twin Cities contained dangerous levels of mercury. The Environmental Protection Agency has warned about the presence of the heavy metal in creams sold in the Chicago area.

California health officials believe there likely are many more people who are using the cream and are unaware of its dangers. The products often enter this country hidden in luggage, or are smuggled across the border. Then the creams are sold under the counter at shops and pharmacies that cater to ethnic communities whose cultural norms lean toward lighter skin as a marker of beauty.

“That is the largest incidence that we’re aware of here in California,” said Dr. Rupali Das, chief of the exposure assessment section at the California Department of Public Health, of the Alameda County cases.

Mercury poisoning can harm the body’s nervous system and kidneys, and even affect personality, health officials say.

The CDC report found that six of those in the study had symptoms consistent with chronic exposure to mercury, including numbness, tingling, dizziness, forgetfulness, headaches and depression. All reported getting their creams either directly from Mexico or from relatives in Virginia who had purchased the creams in Mexico.

Twelve of those with mercury levels found in their urine had not used the creams, but likely were exposed to it by hands that still carried traces of the heavy metal. The youngest among those was an 8-month-old baby.

“It is most harmful on the nervous system and the kidneys and then can also cause changes in personality and a variety of other problems,” said Das, a co-author of the CDC report. “We’re concerned about the harmful effects that mercury can have on children. It can delay their development and they might not catch up — ever.”

The mercury blocks melanin, which gives skin and hair its pigmentation.

But even mild to moderate toxicity due to inorganic mercury can include irritability, difficulty with concentration and memory loss. Insomnia and weight loss can also be side effects and so can tingling in hands, feet or around the lips.

Some of the creams collected and analyzed by California medical officials contained mercury levels 20,000 to 56,000 parts per million. The U.S. Food and Drug Administration allows only trace levels of mercury in creams, or less than 1 part per million.

Latinas, Asians and Filipinas were the predominant users of the creams in California, Das said. For some members of those cultures, traditionally darker skinned people were the laborers who worked outside in the sun, she said, while lighter skin was often considered a symbol of higher social status and wealth.

The family in Alameda used unlabeled face cream in a white plastic jar that was produced in Jalisco or Michoacan, Mexico. They got the cream from a relative in Virginia who has been purchasing the jars from an individual in Mexico.

The highest mercury levels were in the woman and her 4-year-old child. The woman had 100 times the safe level.

The California Department of Public Health advisory said the woman experienced mild to moderate symptoms of tingling in her hands and lips, dizziness, forgetfulness, headaches, depression and irritability and anxiety.

Her 4-year-old child, whose mercury levels were 25 times higher than normal, appeared to have no serious symptoms. Investigators determined the woman used the cream twice a day and her husband once a day for about three years to fade freckles and age spots.

The CDC says inorganic mercury can be ingested, inhaled or absorbed through the skin; then excreted in urine, sweat and breast milk. The half-life of inorganic mercury is one to two months, so mercury levels can increase with repeated application of the creams.

Copyright 2012 The Associated Press.