What Is a Mouth Swab?

A mouth swab is a drug test which detects the presence of the drugs marijuana, methamphetamine, cocaine, phencyclidine, amphetamine, and morphine in saliva. This test, which uses lateral flow immunochromatography, is run by placing the swab in the mouth for several minutes to absorb saliva and then developing it in a testing reservoir for about ten minutes. The mouth swab is a fairly inexpensive and easy-to-use test. This type of drug test is good for detecting recent drug use which may have had an impact on a work-related injury, mistake, traffic violation, or crime, though each swab kit has its own limitations.

Lateral flow immunochromatography is method used to detect the drugs from a mouth swab. The saliva on the swab migrates along special paper infused with a colored reagent. Bound to the color reagent are antibodies against the drugs which are being tested. If the drugs being tested are present in the saliva, they will bind to the specific antibodies and prevent the color reagent from being expressed. When no drugs are present, the colored reagent does not get bound up and is released, coloring the paper.

A test is read by looking for the presence or absence of colored lines next to each drug label in the results window. Each test has a control built in and if the control line appears in the results window, the test was run properly. A colored line next to a drug label means the person being tested is negative for that drug or that the drug has not been used in the last few days. No colored line next to a drug label means the drug has been used. A faint line still means the drug result is negative, and does not indicate a lower degree of drug use.

Mouth swab tests are use by parents checking for drug use in their kids, employers testing employees after a traffic incident, workplace injury or mistake, and for law enforcement. These drug tests are non-invasive, inexpensive, can be administered with minimal training, and adulteration or substitution of the sample is fairly difficult. The cons of this test are that it only measures recent drug use, and frequent drug users who know the test is coming could temporarily abstain to pass this type of test. Adulteration of the results is possible using some hard candy, gum, or mouthwash. To eliminate cheating, the person being tested should be observed for at least 30 minutes prior to the test, during which time nothing should be allowed in the mouth.