An alcohol-based mouthwash can temporarily cause a breath test device to register a positive reading. This is a common concern regarding the accuracy of breath-testing technology. This phenomenon is short-lived and does not indicate actual intoxication, as testing protocols are designed to account for this possibility. The key difference is between alcohol present in the mouth and alcohol absorbed into the bloodstream. While a breath test may be immediately affected, the result will not correlate with the level of alcohol that causes impairment.
The Presence of Alcohol in Oral Hygiene Products
Many common commercial mouthwashes contain a high concentration of ethanol, the same type of alcohol found in alcoholic beverages. This alcohol acts primarily as a solvent and a carrier for active ingredients like essential oils that fight plaque and gingivitis.
Typical alcohol-containing mouthwashes range from 14% to over 27% alcohol by volume. These concentrations are comparable to or even higher than some wines and beers. When swished around the oral cavity, this high concentration leaves a significant amount of residual alcohol vapor on the mucous membranes and soft tissues. This residual vapor is the source of the false positive reading on a breath test, as the device samples the air directly from the mouth.
How Breath Alcohol Testing Measures Oral Contaminants
Breath alcohol testing devices estimate a person’s blood alcohol concentration (BAC) by measuring the alcohol content in their breath. The device assumes the sampled air comes from deep within the lungs, known as alveolar air, where the alcohol concentration correlates with the BAC.
When ethanol is present on the surface of the mouth, it creates “residual mouth alcohol,” which is far more concentrated than the alcohol vapor exhaled from the lungs. When a test is administered shortly after using mouthwash, the device samples this highly concentrated oral alcohol, interpreting it as if it were coming from the lungs. This oral contamination leads to an artificially elevated reading that does not reflect the subject’s actual level of intoxication. Modern evidentiary devices may use sophisticated technology to detect a rapidly falling alcohol concentration, but they can still be fooled by the high initial spike.
Time Needed for Alcohol Levels to Clear the Mouth
The residual alcohol left in the mouth from products like mouthwash dissipates very quickly through evaporation. Scientific studies confirm that the high concentration of mouth alcohol typically clears from the oral cavity within a short period, usually becoming undetectable in the breath within 10 to 15 minutes after use.
This rapid dissipation is the reason many law enforcement and workplace testing protocols mandate a 15-minute observation period before administering a breath test. This waiting period is specifically designed to eliminate false positives caused by oral contaminants, including mouthwash or breath sprays. During this time, the subject is observed to ensure they do not put anything into their mouth. If an initial test yields a high reading due to mouth alcohol, a retest after the observation period should show a significant drop, often to zero if the person is sober.
Steps to Prevent a Misleading Test Result
The most reliable way to prevent a misleading breath test result is to use oral hygiene products that are labeled as alcohol-free. Many brands now offer effective mouthwash formulations that use alternative antimicrobial agents, removing the source of the false positive entirely.
If you must use an alcohol-containing mouthwash, ensure there is a sufficient time gap between use and any potential breath test.
Prevention Steps
- If a test is imminent, immediately rinse the mouth thoroughly with water multiple times to wash away residual alcohol.
- If tested and receiving a positive reading, inform the administrator or officer of your recent use of the oral product.
- Request a retest after the standard 15-minute observation period, which is designed for this exact scenario.
- Remember that alcohol from mouthwash does not enter the bloodstream in any meaningful amount, meaning a blood alcohol test would be unaffected.