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Does drinking mouthwash make you fail a breathalyzer test?

Launcher gethin
Status Closed Mediated Closed 3 years, 5 months ago
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Organic chemistry alcohol


I've heard that if you're being breathalyzed while driving a car you can blow over the limit if you've been drinking mouthwash. I've also heard that you can show a lower reading if you have a massive drink of water before being tested. Are either of these true?

Answers (3)

  • Icarus
    Aug 14, 2011

    Well, yes and no. Many brands of mouthwash and breath sprays contain alcohol as an active ingredient and swishing mouthwash or spraying a breath spray will register a result higher than the legal limit of .08 on a breathalyzer test but only for a short time. This is caused by what is termed “raw-mouth alcohol” where alcohol lingers in the mouth and trigger a false positive result on the breathalyzer.[1]

    But as mentioned, the effect only lasts for a few minutes. Police officers are required to conduct a 15 minute observation before taking a sample and breathalyzers do not measure the smell of alcohol in your mouth but instead measures deep breath alcohol which is proportional to the alcohol in your bloodstream.

    Breath sprays on the other hand can last a bit longer, often registering a .50 on the breathalyzer test for up to 20 minutes after using one (thus using a breath spray to mask the odor of alcohol in your breath is a really bad idea) [2]

    As for drinking water, as only about 5% of the alcohol you drink is expelled through urine[3], drinking lots of water may cause you to want to go to the bathroom, any effect this has on your blood alcohol content is pretty negligible.

  • nathanww
    Jul 20, 2011

    While mouthwash does raise the breath alcohol concentration, the effect is very short-lived, and a person who has not consumed any alcohol will not have a legally-significant breath alcohol concentration 10 minutes after rinsing with the mouthwash.


  • einstein
    Jul 30, 2011

    According to the following experiment conducted on three individuals, mouthwash does not register in a breathalyzer test more than 2 minutes after washing your mouth out with it:

    This suggests that unless you are practising good dental hygiene while you're driving, you should be A-ok!

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Sorry, are you asking about actually ingesting the mouthwash, or just rinsing your mouth with it? Mouthwash is typically not ingested.

Asked by nathanww on Jul 20, 2011


Rinsing your mouth thoroughly with it - I've heard that the residual alcohol content is high enough to effect the reading


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