Surprising breathalyser triggers (even when you haven't been drinking)
Get the details on which ethanol-containing items might trigger a breathalyser test
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Some foods, drinks and everyday products can leave trace amounts of ethanol in the mouth, which could briefly show up if a test is taken shortly after use.
Our new research reveals how some foods, toothpastes or cough syrups can lead to false breathalyser readings.
Whether you're driving an Audi, BMW or other brand, it's always important to be under the limit behind the wheel.
Ben Welham, our motoring expert, says: “Most people are surprised to learn that something as innocent as a hot cross bun could briefly show up on a breath test.
“It won't get you in trouble, but it's a good reminder of just how sensitive these devices can be.”
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Everyday foods and products that can briefly affect a reading
Some items are more likely to cause this than others, particularly anything linked to fermentation, high sugar content or alcohol-based ingredients.
Hot cross buns
Made with yeast, sugar and dried fruit, hot cross buns can produce tiny amounts of ethanol as they break down.
One driver recorded a brief positive reading immediately after eating one, despite not consuming any alcohol.
These readings typically return to zero within minutes as any residue clears from the mouth.
Jackfruit
Popular in many plant-based diets as a meat alternative, jackfruit contains high levels of natural sugar, particularly when overripe. As the fruit ripens further, those sugars can begin to ferment and produce small amounts of alcohol.
In one reported case in India, bus drivers triggered positive breathalyser readings before starting work after eating overripe jackfruit.
The results were temporary and not linked to intoxication, but they highlight how naturally fermenting foods can impact readings.
Toothpaste and mouthwash
Some types of mouthwash, and some toothpaste formulations, contain alcohol or alcohol-based compounds.
Studies have shown that alcohol-based mouthwash can temporarily elevate breathalyser readings if used shortly beforehand, as residual ethanol remains in the mouth before dissipating quickly.
Cough syrups and liquid medicines
Some liquid medicines, particularly cough syrups and cold and flu remedies, contain small amounts of alcohol.
In some cases, these formulations can contain measurable levels of ethanol, which can leave temporary residue in the mouth if taken shortly before a test.
Hand sanitiser
It’s not just eating or brushing your teeth that can lead to an unexpected breathalyser reading.
Using hand sanitiser just before taking the test might also show up, according to research published in the American Journal of Infection Control.
In controlled tests, readings briefly increased after ethanol-based hand sanitiser was used shortly before testing, before returning to normal within minutes.
How breathalysers actually work
Breathalysers are designed to measure blood alcohol level (BAC), which authorities use to gauge a driver’s level of intoxication.
When we drink alcohol, it enters the bloodstream, and some of that alcohol evaporates into our lungs as the blood moves through them.
A breathalyser measures the concentration of ethanol (the type of alcohol in alcoholic drinks) in your breath using a chemical reaction, then does a calculation to determine your BAC.
“The key difference is where the alcohol is coming from,” says Ben. “Breathalysers are designed to measure alcohol in the bloodstream, but in some situations, they can briefly detect alcohol in the mouth instead. That’s why proper testing procedures include a waiting period.”
What drivers should know
The chances of everyday items causing a meaningful breathalyser reading are very low, especially under proper testing conditions.
Officers typically wait around 15 minutes before carrying out a formal test to allow time for any food, drink or residue in the mouth to clear.
Still, it’s a useful reminder of how sensitive breathalysers can be immediately after eating, drinking or using certain products.
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