Introduction (JCREATION | Shutterstock)

There are times in life when you just need to take a pee. For example, you may be required to take a drug test before starting a new job. But these tests aren't foolproof: Some harmless, everyday substances can trigger false-positive drug results. Below we take a look at nine substances that can give you a weird positive result for illegal drugs. Coca Tea (BonnieBC | Shutterstock)

Drinking coca tea may cause false positive results for cocaine. Popular in South America, this tea is made from the leaves of the coca tree, the same source of cocaine. In a 2006 study, five people drank coca tea before taking a drug test. All subjects tested positive for cocaine metabolites 2 hours after drinking tea, and 3 subjects still tested positive for cocaine 36 hours after drinking tea. The researchers concluded: "Healthcare workers should consider a history of drinking coca tea when interpreting uremia results." KDSPE cold medicine KDSPs KDSPE (Image credit: Wave Media/Shutterstock) KDSPs some Over-the-counter cold medicines contain ingredients that may cause false-positive results. Amphetamines. For example, according to a 2010 retrospective study,

and past use of the nasal decongestant Vic's inhaler led to false positives for amphetamine, brompheniramine, which is used by some cold and allergy drugs of antihistamines, which can interfere with methamphetamine tests, causing false-positive results, according to a 2008 review study. The author of the review wrote that Vick's inhaler contained L-methamphetamine, a chemical "mirror image" of methamphetamine. However, new drug tests can differentiate between methamphetamine and the chemicals in Vic inhalers, so cold medicines no longer trigger false positives, comments

Secondhand Smoke from Marijuana (Stanimir G. Stoev | Shutterstock)

In extreme cases, a 2015 study showed that sharing a room with someone who smokes marijuana may result in a positive marijuana test. In that study, six people smoked marijuana in a sealed room while six non-smokers sat next to them. An hour later, several non-smokers tested positive for marijuana in sensitive tests that can detect tetrahydrocannabinol, or THC, the active ingredient in marijuana, at concentrations of 20 to 50 nanograms per milliliter," these results said. showed that extreme marijuana smoke exposure can produce positive urine tests at commonly used cutoff concentrations." However, the researchers note that in real-world settings, these positive tests are likely to be rare because testing takes place several hours after exposure. By doing so, non-smokers may become aware that they have been exposed to second-hand marijuana smoke. Antibiotics

Certain antibiotics, including rifampicin and fluoroquinolones, may cause false-positive opioid results. In one case reported in 2002, a 7-year-old boy from Lebanon tested positive for opiates when he presented to the emergency room. However, it was later determined that the rifampin he was taking interfered with his drug test. Baby Soap (Shutterstock Baby Bath)

Certain soaps used in hospitals to wash babies soon after birth may cause babies to test positive for marijuana on some newborn screening tests, according to a 2012 study Research. (These tests are used to determine if mothers are using drugs during pregnancy.) Health care providers have found that using these soaps (including Johnson & Johnson Head to Toe Baby Wash, Johnson & Johnson Bedtime Bath, CVS Overnight Baby Wash, Aveeno Soothing Soothing Cream Infants washed with body wash and Aveeno shampoo had positive results on a urine drug screening test for THC, the active ingredient in marijuana.

In that study, Chers said they weren't sure why soap caused false positives. Researchers say it could be that some compounds in the soap have a structure that is partially similar to THC, or it could be that chemicals in the soap change the way the test works. As for how the soap got into the urine sample, the researchers suspect that some residual soap on the baby's skin was washed into the child's urine sample. Ibuprofen Generic ibuprofen tablets are usually brownish-red in color.

(BW Folsom | Shutterstock)

Taking NSAIDs, such as ibuprofen, can in rare cases cause false-positive results for several medications. In a study conducted in 1990, 60 people took ibuprofen at several different doses (one dose of 400 mg/day, three doses of 200 mg/day, or three doses of 400 mg/day, depending on the experimental group to which they belong). One patient taking the highest dose of ibuprofen (1,200 milligrams per day) tested positive for cannabinoids, a compound in marijuana. Another patient tested positive for barbiturates, used for anti-anxiety or sleep medications. The researchers concluded that the findings "showed a small likelihood of false positives" after taking ibuprofen. Hydration (Photo of Gin Hydration via Shutterstock)

Hydration contains small amounts of quinine, a A drug used to treat malaria. Quinine is also sometimes mixed with street drugs, so it can be an indicator of illegal drug use. In a 1989 study, researchers at Brown University in Rhode Island reported that positive urine test results for quinine were caused by drinking rehydration in mixed drinks. HIV Drugs (Nenov Brothers Images/Shutterstock)

An antiviral drug used to treat HIV can also cause people to test positive for marijuana. For example, in 2006, researchers reported interesting findings from a study of 24 people who took Alfavirenz (brand name Sustiva). At the start of the study, all participants tested negative for THC, but after taking efavirenz, they all tested positive. Researchers say Effavirenz may interfere with the way the test works. Poppy seeds (tRufelka Elena | Shutterstock)

Poppy seeds naturally contain the compounds morphine and codeine, so consuming some products containing poppy seeds may trigger false-positive results for these drugs. In a 1987 study, five members of a lab baked cookies containing about 1 teaspoon (5 ml) of poppy seed filling from a grocery store. Two hours after eating several cookies, all lab members tested positive for opiates. According to a 2008 retrospective study, the drug's concentration exceeded 300 nanograms per milliliter, the lowest limit used in testing.

In 1998, the Department of Health and Human Services changed the limit to 2000 ng/ml to avoid false positive results due to consumption of poppy seeds. However, the researchers say, most labs continue to use lower cutoffs