Using mouthwash can impact the accuracy of a breathalyzer test. Mouthwash can temporarily affect breathalyzer readings, potentially causing confusion and complications during an alcohol screening.
The Science of False Positives
Many common mouthwash products contain alcohol, primarily ethanol, as an active ingredient. The concentration of alcohol in these oral rinses can be significant, often ranging from 0% to 27% by volume, with some brands like Listerine containing over 20% alcohol. This level of ethanol is comparable to or even higher than the alcohol content found in many beers and wines.
Breathalyzers are designed to estimate a person’s blood alcohol content (BAC) by measuring the alcohol vapor in their deep lung air, known as alveolar air. When alcohol from mouthwash is present in the oral cavity, it creates “mouth alcohol.” This residual alcohol can temporarily confuse the breathalyzer device. The device cannot distinguish between alcohol originating from the deep lungs, which reflects systemic intoxication, and alcohol lingering in the mouth from external sources. If a breathalyzer test is administered too soon after mouthwash use, the residual ethanol can lead to an artificially elevated or false positive reading.
How Long the Effect Lasts
The effect of mouthwash on breathalyzer readings is temporary. The alcohol from mouthwash quickly dissipates from the mouth and oral cavity, as it is not absorbed into the bloodstream in the same way as ingested alcohol. Studies have shown that breath alcohol measurements can spike significantly immediately after mouthwash use, then decline rapidly.
Typically, the effect of mouthwash on a breathalyzer reading dissipates within 10 to 20 minutes. Rinsing the mouth thoroughly with water after using mouthwash can help to further reduce any residual alcohol and accelerate its clearance. This transient nature of mouth alcohol explains why specific protocols are in place for breath testing.
Navigating a Traffic Stop
Law enforcement officers are generally aware that mouthwash can influence breathalyzer results. To ensure accurate readings, police protocols often include a 15 to 20-minute observation period before administering a breathalyzer test. During this time, the individual is observed to ensure they do not eat, drink, regurgitate, or place anything in their mouth that could introduce mouth alcohol, allowing any residual mouth alcohol to dissipate naturally.
If you are pulled over and have recently used mouthwash, calmly explain this to the officer. If a breathalyzer is administered sooner than the recommended observation period and you believe the reading is inaccurate due to mouthwash, you can politely request a retest after a proper waiting period. In situations where a breathalyzer result seems erroneous, options for alternative testing, such as blood or urine tests, measure alcohol directly in the body’s systems. Officers may also conduct field sobriety tests, which assess physical coordination and impairment independent of breath alcohol content.