It wouldn’t be a bad idea to carry a pack of gum with you to work on a daily basis if you’re concerned about surprise swab tests.

Avoid using alcohol-based mouthwashes, though, as they can lead to a false positive result for alcohol abuse.

Also avoid taking cough suppressant medication that contains codeine.

Chemicals get into your saliva from your bloodstream, which can’t be “flushed out” the same way. Still, there’s no harm in upping your hydration and saliva output for 48–72 hours before the test.

Brushing your teeth thoroughly and consistently won’t work any miracles, but it will ensure that old oral fluids aren’t built up in your mouth.

The effect this will have will be small and short-lived. [9] X Trustworthy Source PubMed Central Journal archive from the U. S. National Institutes of Health Go to source But it’s also one of the easiest steps you can take.