Chemicals in Baby Shampoos Lead to False Marijuana Positives

June 20, 2012— -- Exposure to trace amounts of baby soaps and shampoos, commonly stocked in grocery stores and pharmacies across the county, are leading newborn babies to test positive for THC, the active ingredient in marijuana, a new study finds.

A hospital in North Carolina became concerned recently when a high number of its newborns tested positive for marijuana exposure. When researchers began looking into it, they found the culprit was chemicals found in baby soaps, including those manufactured by Johnson & Johnson, Aveeno and CVS brand products.

Dr. Catherine Hammett-Stabler, lead study author at the University of North Carolina, Chapel Hill, said that at first researchers were unable to pinpoint what was causing the urine tests to come back positive for marijuana.

"We went up to the nursery, followed the nurses and the staff around to identify everything that was done, everything that was essentially touching those babies' skins, could possibly come into contact with the urine that we were subsequently testing," she told ABC News. "We were really surprised when we found it was the soaps were the culprit."

Mixtures of drug-free urine and various commercial products and materials that commonly contact newborns were used in the study, according to the abstract published by the National Center for Biotechnical Information.

The study ultimately found that certain chemicals found in these soaps and shampoos -- including polyquarternium-11 and cocamidopropyl betaine -- can trigger the positive THC results.

Products that led to the false positives included Johnson & Johnson's Bedtime Bath, CVS Night-time Baby Bath, Aveeno Baby Soothing Relief Creamy Wash and Aveeno Baby Wash & Shampoo.

The researchers said they believe that trace amounts of the chemicals -- 0.1 milliliters or less -- were coming from the soaps, washing off the babies' bodies, and finding their way into the urine samples used for the study.

Testing newborns for marijuana is fairly routine, especially in situations where the mothers are considered high-risk. Dr. Carl Seashore, a co-author of the study, told Time magazine that one of the reasons to conduct the research was to ensure that no mothers were falsely accused.

"[The researchers] do not want to be falsely accusing anybody. They want to correctly identify situations that need additional intervention or social services actions for the protection of the baby," Stabler told the magazine.

Dr. John Spangler, an associate professor of family and community medicine at Wake Forest University School of Medicine in Winston-Salem, N.C., agreed that more discriminating tests are needed.

"This has profound implications," Spangler said in an email to ABC News. "Think about being a mother who knows she has never been exposed to illicit drugs. How does she fight against the supposed 'objective' lab test?"

Spangler cited mothers who had been arrested based on tests of their babies, but insisted that they had never smoked marijuana.

"On the one hand, we must screen babies' urine to protect them from harmful environments, such as households where drugs are used," he said. "On the other hand, this study makes clear that such screens are plagued by known and unknown factors that can result in false positives."

Researchers who conducted the University of North Carolina study said that labs need to be aware of this potential source for false positive screening results, and understand that "sources of error are not confined to the laboratory walls."

They also said that the research demonstrates the need for active involvement in the "total testing process" to reduce false results and, in some cases, needless legal action.

ABC News Radio contributed to this report.