Baby Soap Triggers False-Positive Test Results For Marijuana

Lawrence LeBlond for

Marijuana screening tests performed on newborns can be contaminated by use of common baby soaps and shampoos that give false-positive results, a new study by researchers at the University of North Carolina, Chapel Hill, has found.

According to the researchers, just a minute amount — 0.1 milliliters or less — of the products found in a urine sample was enough to give the positive result. The results could prove frightening for parents, who, in some states, may have their children taken away because of a false-positive screening.

The Chapel Hill team began studying the issue after an unusually high number of newborns in the nursery began testing positive for exposure to marijuana. Such tests are not uncommon, being given to newborns of women who are considered at high risk of drug use. At Chapel Hill, between 10 and 40 percent of newborns are tested.

“We really did this to help protect families from being falsely accused,” study co-author Dr. Carl Seashore, a pediatrician in the U.N.C. Chapel Hill newborn nursery, told My Health News Daily.

The team found five baby products that trigger the false positive results: Aveeno Baby Soothing Relief Creamy Wash, Aveeno Baby Wash Shampoo, CVS Night-Time Baby Bath, Johnson & Johnson´s Bedtime Bath, and Johnson & Johnson Head-to-Toe Baby Wash.

Some other baby products tested, including CVS Baby Magic and some standard hospital gel soaps, also indicated presence of marijuana metabolites when tested, but were not sufficient enough to produce a positive result on a screening test, according to the team´s standards.

Seashore said the problem is almost certainly not limited to baby products. He and colleagues found that most soaps and shampoos that contain polyquaternium-11 and cocamidopropyl betaine elicited positive marijuana test results.

The research team said they do not yet know why these chemicals interfere with the test´s function, however, they noted, they do not cause symptoms of marijuana exposure in children. They believe that tiny amounts of the chemicals were simply washing off the babies´ skin into their urine samples and contaminating the tests.

While more sophisticated tests can easily distinguish between true and false positive results, most hospitals do not use them because they are costly. Still, it is unclear why hospitals test infants for marijuana exposure in the first place.

Twelve states designate prenatal exposure to any illegal drug as child abuse, even though there is no scientific evidence that connects marijuana-use with abuse. And it remains unclear if the benefits of such tests, if any, justify the potential harm it can cause on families.

“If the issue is that the mother broke the law and therefore the child should be removed, we might want to consider going after mothers who exceed the speed limit while driving,” Carl Hart, an associate professor of psychology at Columbia University and author of a leading text on drug effects, told TIME. “Of course, this is ridiculous.”

Removing children from their home at birth because of a positive marijuana test is immediately and inexorably harmful, Richard Wexler, executive director of the National Coalition for Child Protection Reform told TIME’s Maia Szalavitz.

“Even when the test is accurate, there is no evidence that smoking pot endangers children,” he said. However, he added, “there is overwhelming evidence that needless foster care endangers children.”

The odds of abuse and neglect are much higher in foster care, Wexler said. “These infants are being taken from homes where there is no evidence of abuse, and placed in a situation where the odds of abuse are at least 1 in 4. The odds of this kind of separation doing emotional damage are nearly 100 percent. Children risk enormous emotional trauma when they are torn from their mothers during a crucial period for infant-parent bonding.”

Wexler noted that one study of infants exposed to cocaine in the womb found that their physical growth and development increased when they remained with their biological parents, compared with those who were removed from the home. “For the foster children, being taken from their mothers was more toxic than the cocaine,” he said.

While maternal cocaine use during pregnancy has been linked with subtle developmental problems in children, for the most part it is no worse than women who smoke cigarettes during pregnancy, and doing both can increase the risk of preterm birth and stillbirth. But neither are as dangerous as alcohol, which can cause irreversible intellectual disability.

The evidence on marijuana use during pregnancy is inconclusive — some studies have linked marijuana use to reduced fetal growth and behavioral problems, while others have found no effect whatsoever.

Paul Armentano, deputy director of the National Organization for the Reform of Marijuana Laws (NORML) notes that, since immunoassay drug test results only indicate the presence of a simple chemical reaction, not the actual drug itself or its metabolite, these tests must always be confirmed.

But, he added, most of these drug tests provide very little useful information about whether someone actually used a particular substance, when they last used a particular substance, or whether they were impaired at the time they were tested.

So be watchful and keep these findings in mind next time you have to take such a drug test, says Armentano.

If you also consider the risks of false-positive results due to bath soaps and shampoos, it doesn´t make sense to continue these types of marijuana tests, especially on newborns.