Will mouthwash affect alcohol test results?

Yes, in some circumstances a mouthwash containing alcohol can affect your alcohol testing results.

Because some mouthwashes contain the same alcohol as an alcoholic beverage, if you have used this type of mouthwash immediately prior to taking a breath alcohol test, the test may detect the residue of the alcohol in your mouth. The residual alcohol from rinsing with mouthwash dissipates within 10 to 15 minutes after exposure. However, actual ingestion of mouthwash, or any other substance containing ethanol, can result in a positive alcohol test and even intoxication.

Nonbeverage Ethanol

Many brands of mouthwash and other products such as breath sprays, cough medicines, and hand sanitizers contain the same ethyl alcohol that is found in alcoholic beverages. This nonbeverage ethanol is denatured, or altered, to make it unpalatable or otherwise undrinkable. Usually denaturing takes the form of adding other ingredients to prevent consumption of the substance. For instance, Listerine mouthwash contains active ingredients such as eucalyptol and methyl salicylate that have an unpleasant flavor. Despite this alteration, the ethanol itself that is contained in these products remains unchanged and has the same effect on your body, and an alcohol test, as an alcoholic beverage. In fact, the alcohol concentration in some mouthwashes reaches as high as 26.9%. At 54 proof, this alcohol content is well above the content of your average beer.

Rinsing Your Mouth

Absent addiction, most people don't intentionally consume nonbeverage alcohol. However, some people might think that rinsing your mouth with mouthwash before a breath alcohol test will either mask the presence of alcohol in their system or cause the test results to be invalid.

The opposite is true. When you rinse your mouth with a substance containing alcohol, it is absorbed into your saliva and the tissue of your mouth. For the first 10 to 15 minutes after rinsing, this absorption may cause a breath alcohol test to detect a higher concentration of alcohol (breath alcohol content) than would otherwise be detected. Because this effect is well known, procedures for an evidential breath test (EBT) require you to refrain from drinking or eating for at least 15 minutes before your breath alcohol test. By observing this waiting period, the test administrator can be assured that your test results are not contaminated by residual mouth alcohol.