Dreamland Magazine

6 Surprising Things That Can Trigger A False Breathalyser Reading

Random breath tests have always terrified me. What if I blow a positive reading even though I haven’t been drinking? What if alcohol has somehow snuck its way inside my body!? What if my body is just naturally alcoholic?

These fears sound ridiculous, but for the occasional unlucky person, they become reality. A wide variety of illnesses, medications and foods are known to sporadically trigger a false reading on a breathalyser.

We all know foods prepared with alcohol, such as a boozy tiramisu or a box of liqueur chocolates, are going to result in alcohol in our body and on our breath. But here are six other things that you might not expect to be capable of tricking a breath test into thinking you’re drunk.

1. Diabetes

A common issue for diabetics is hypoglycemia (when their blood sugar drops too low.) Other than causing dizziness, shaking, headaches and a range of other symptoms akin to drunkenness, hypoglycemia causes the level of acetone in the body to spike.

Acetone, known for being the chemical in cleaning products and nail polish remover, is produced during the human body’s metabolic functions and is present in blood and urine.

During hypoglycemia, the body produces more acetone to combat the lack of glucose, leading to the greater concentration of acetone in the breath of diabetics. This has been estimated to cause BAC readings of up to 0.06 – high enough to blow over for drink driving.

2. Fasting or extreme dieting

This is another acetone one. Fasting or diets that induce ‘ketosis’ (you might have heard of this on some of those TV ads for weight loss supplements) cause greater acetone levels in the body.

Basically, ketosis is when the body breaks down fat really fast, turning it into fatty acids which are then converted into things called ketones.

These are used to create energy for the body in place of glucose – it is essentially a human’s energy back-up plan. Acetone is a component of ketones’ structure, and when they are used for energy the acetone is released into the body.

Usually you can smell acetone on the breath of people with a high concentration of it, so if you’re looking to take precautions, get someone to sniff your breath before you get behind the wheel.

3. Mouthwash

Thought you’d clean out your mouth to make sure no trace of last night’s alcohol is left? Well mouthwash might not be the best idea.

Many brands of mouthwash contain alcohol as a key ingredient, often around 20 per cent. This alcohol lingers on your breath for a short period of time and can trigger a reading on a breathalyser.

Luckily, as mouthwash only leads to mouth alcohol rather than alcohol in the blood stream, it can only cause a breath test reading for the first 10 or so minutes after rinsing your mouth. So maybe just leave a little time between your oral health routine and hitting the road.

4. Cold and flu medications

You’ve got a bad cough so thought you’d take some cough syrup before you drive.

It would be so dangerous if you had a coughing fit while driving. Good safe choice, you think… Until you get to a breath test and blow a reading.

Cough syrups and medications for treating cold and flu symptoms often contain small amounts of alcohol. When they are ingested, the alcohol can linger in the mouth and be present on your breath, ultimately causing a breathalyser reading above zero.

If you find yourself in this situation, just explain to the police officer what medications you’re taking and perhaps launch into a coughing fit so they can tell you’re not making it up.

5. Bread and bakery products

Here’s a story: a man walked up to my local Bakers Delight and bought some pizza rolls. He ate the pizza rolls. He got into his car and drove off. He arrived at a random breath test. No stress, the man thought, I haven’t been drinking today.

*blows into breathalyser*


Breathalyser registers 0.25 BAC.


It turned out that this man’s false breathalyser reading was caused by the pizza rolls – more specifically, the yeast in the rolls. When yeast ferments, it becomes alcoholic (think BEER). This fermentation can happen inside the body and hence confuse a breath tester.

This scenario is more likely to occur in people who have a rare medical condition called ‘auto-brewery syndrome’ (which is a sick as name – imagine turning up to a party and explaining how your body is a brewery). The condition means the body ferments so much yeast from food you’ve eaten that it produces enough ethanol to make you feel drunk (less sick side effects).

Whilst this syndrome technically triggers a breathalyser reading without drinking, sufferers are still experiencing symptoms of drunkenness so probably shouldn’t be driving.

Unless this is all some ploy by health experts to get us to stop eating bakery treats. Hmm.

6. Ripe fruit

Fermentation also occurs naturally as fruits ripen. Yeast grows inside and on fruit over time and this combines with the sugar in the fruit to ferment into ethanol. According to studies in 2002 and 2004 by Robert Dudley of the University of California in Berkeley, over ripe fruit contains 4.5% ethanol on average.

Depending on how much you eat and how soon you drive, this can cause a false reading on a breath test.

Moral of the story: eat ripe fruit if you’ve run out of alcohol. And yes, I know that sounds like something your mum made up to make you eat more fruit.

Seriously though…

All these things are pretty unlikely to lead to a false breathalyser reading. They’ve all been known to happen and a little bit of science backs them up. But really, just don’t drink and drive. That’s the real issue. It’s okay if you want to eat bread and drive.

This article was written by April Austen

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