According to Medilink UK, the University of Birmingham created a test called Saliva SmokeScreen to test for nicotine exposure. The saliva test actually checks for cotinine, a byproduct of nicotine. Creator Dr. Graham Cope notes it could determine whether someone has smoked within the past three days.
To take the test, a person needs to either spit in a container or have the inside of his mouth swabbed by a doctor or lab technician, according to GFC Diagnostics. The Saliva SmokeScreen test uses a strip that is dipped into a saliva sample, but more precise results come from a mouth swab that is sent to a lab for testing.
The American Association for Clinical Chemistry says that doctors and employers usually test for nicotine and cotinine in saliva to check on a patient's health or to follow insurance guidelines. For example, some health insurance companies require random nicotine testing for members to be eligible for lower insurance costs. Doctors can also use the test to help patients quit smoking and learn more about their health histories.
The reason labs test for cotinine rather than nicotine is that nicotine leaves the body much quicker, notes the Centers for Disease Control and Prevention. After someone ingests nicotine through smoking, chewing or even touching tobacco, the chemical is absorbed into the body. Cotinine remains in the body after nicotine breaks down.