The general procedure for a saliva drug screen / oral fluid-based drug screen is to keep the person from drinking or inserting anything in the mouth for a period of time (typically about 15 minutes). A collection of saliva is then obtained and either mixed with chemicals or placed onto a color-test strip in order to determine the presence of alcohol or other drugs. This general procedure is also used to test levels of hormones and other body chemicals.
This test was once widely used for the testing of illegal drugs but it is now declining. The time period during which alcohol and drugs can be detected by this method is relatively low, around 3 hours to 4 days maximum. There are several products marketed to destroy the toxins in the market to create a false negative with this test.
This test also has no nationally accepted standards or cutoff concentrations for detection, making results greatly dependent on the specific product used for the test. This can make results less reliable and unacceptable for legal cases.