- Some legal over-the-counter drugs (such as Vicks VapoInhaler ) and some foods (such as poppy seeds) may cause a positive screening drug test. This might look like someone used illegal drugs (such as methamphetamines or opiates) when they did not. Researchers are studying how the body handles chemicals that may test like illegal drugs and for how long they may be detected in the body. Blood, saliva, and urine samples will be collected. This study may help improve the effectiveness and accuracy of drug tests.