Chemicals in Personal Care Products Linked to False Positives for Marijuana

Chemicals used in soaps, shampoos and other personal care products have caused some drug screenings to incorrectly test positive for marijuana. Multiple newborns in a North Carolina hospital tested positive for tetrahydrocannabinol (THC), the active component in marijuana, after chemical residue from baby soaps and shampoos contaminated the infants' urine samples.

Researchers at the University of North Carolina, Chapel Hill conducted the study after the hospital reported a record number of positive tests in July 2011. Researchers concluded that chemicals used in over-the-counter soaps and shampoos, from brands such as Johnson & Johnson and Aveeno, were causing the positive results. The samples became contaminated by soap residue on the babies' skin during collection.

"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," said Dr. Catherine Hammett-Stabler, lead author on the study, in an interview with ABC News. "We were really surprised when we found it was the soaps were the culprit."

The ingredients causing the reaction include polyquarternium and cocamidopropyl betaine, which are commonly used in soaps, shampoos, hand sanitzers, hair styling products and cosmetics for their antimicrobial and emulsifying properties. The chemicals are not harmful, do not cause effects similar to THC and did not enter the bodies of any of the infants tested. Researchers were unsure why they caused the samples to test positive, although they were able to determine that as little as 0.1 milliliter was enough to trigger the false positive.

Dr. Carl Seashore, co-author of the study, said the researchers did not want to implicate any of the personal care manufacturers, and reaffirmed that all of the products and chemicals studied are safe to use. The purpose, he told My Health News Daily, was to protect families from being unjustly persecuted as the result of potentially incorrect testing.

Seashore explained that infants born to women considered at a high risk for drug use are often screened for marijuana. A positive test can lead to accusations of child abuse and an investigation by child welfare services. "We really did this to help protect families from being falsely accused," he said.