It’s a reality in many immigrant communities: some dark-skinned people use products to make their skin lighter.

But the products aren’t always safe. In April, 40 people in six Orange County homes, mostly in Santa Ana, were exposed to dangerous levels of mercury after someone in each household used skin lightening cream laced with the toxic metal, health officials said. At least one young girl was hospitalized with symptoms of mercury poisoning.

State and local officials responded in an effort to contain the damage, but they encountered hurdles that highlighted the challenges of responding to a public health emergency involving an unregulated product in an immigrant community. Though they haven’t become aware of any additional cases of mercury poisoning, health officials fear other Latina women and their families could still be at risk and not know it.

Officials said they first became aware of the contaminated creams after the hospitalized girl’s tests confirmed mercury poisoning. Investigators interviewed her mother, and learned she had been using a skin lightening cream that contained nearly 40,000 times the allowable limit for mercury in cosmetics. The toxin made its way onto bedding, clothes and furniture, turning the home into a hazardous waste site.

The interview also revealed that the woman had gotten the cream from a friend.

"And that friend had given it to other people," said Dr. Helene Calvet, a health officer with the Orange County Health Care Agency. "And that’s how we found most of them knew each other. And some of it was word of mouth, like, 'Hey, your skin is very beautiful, what are you using?'"

Mercury is an effective skin-lightener because it inhibits production of the skin pigment melanin. Mercury-laced creams have popped up in a variety of immigrant communities, from Filipino to Chinese to Indian.

Investigators of the Orange County cases determined that the creams had come from Mexico. The creams appeared to be homemade, in little jars with hand-typed labels. Some people in the Latino community call them "clandestinas" – clandestine products that cross the border in people’s suitcases and get passed through the community by word of mouth.

"It’s not your typical commercial chain," said Lori Copan, a researcher with the California Department of Public Health. She said that makes it difficult for officials to respond and try to contain the damage. In other cases, Copan said, the state can cut off the flow of dangerous foreign products by placing an embargo on their importation.

But that’s only "if we’re able to identify a manufacturer or distributor," she said. "Because this is really person-to-person, we’re not able to do that."

The informal market means health officials also don’t know how much toxic cream might still be out in the community, being slathered on by people oblivious to its dangers.

Copan said she suspects there may be a lot.

"We believe we’re looking at just the tip of the iceberg," she said.

So health officials have had to rely on outreach to try to track the creams down and discourage people from using them.

They issued a public health alert and notified doctors to be on the lookout for symptoms of mercury poisoning, which can include brain, nerve and kidney damage. They also did interviews on Spanish-language news programs.

Nora Pacheco, a Mexican immigrant living in Los Angeles, said that’s how she heard about the contaminated creams. Pacheco’s daughter owns a shop that sells balms, herbs and tree barks imported from Latin America, usually used for pain or for spiritual ceremonies.

"Women come in and ask if I sell lightening creams," she said, standing in front of a shelf full of ointments. "I tell them, no, I don’t, so they keep asking around."

Pacheco said her own niece has considered using lightening creams.

"She says, 'Oh, my skin color is so ugly, I'm so dark. I'd like to use something to make it whiter,'" Pacheco said. "But personally, I would never use them. Those creams scare me."

Health officials recognize that for each person like Pacheco, there are others for whom the allure of lighter skin could lead them to a dangerous product.

"That's a pretty pervasive belief throughout the world, that clear and light skin is a good thing to have," said Calvet of the Orange County Health Care Agency.

But as the recent cases have illustrated, that desire for light skin can come at a cost, she said. In Orange County, it harmed people’s health, and left public health officials scrambling to respond.