What Besides Alcohol Can Set Off a Breathalyzer?

Mouthwash, breath sprays, cough syrup, asthma inhalers, diabetic ketoacidosis, severe acid reflux, kombucha, and some industrial solvents can all register on a breath test even when you haven’t been drinking, so the list of things besides alcohol that can set off a breathalyzer is longer than most people realize. The practical risk is another matter. Modern evidential instruments used by police are far more selective than the cheap devices sold online, and standard testing protocols are designed to catch most interferences before a reading becomes evidence.

Mouth Alcohol Is the Biggest Culprit

Breathalyzers are built to measure alcohol from deep lung air, which tracks your actual blood alcohol concentration. When alcohol is sitting in your mouth or throat instead, the device reads it as if it were all lung air and the number spikes. This “mouth alcohol” effect is the single most common source of artificially high readings.

Mouthwash, Breath Sprays, and Cough Syrup

Listerine contains roughly 27% alcohol and Scope about 19%. A study measuring breath alcohol after rinsing with Listerine recorded readings as high as 240 mg/dL (equivalent to a 0.24 BAC) two minutes after use, which is three times the legal limit from mouthwash alone. Those readings dropped below 0.08 within ten minutes and fell to zero shortly after.¹ The researchers concluded that mouthwash wouldn’t realistically threaten breath test accuracy under normal circumstances, but using it immediately before a test could significantly inflate the result.

The same mechanism applies to alcohol-based breath sprays and to over-the-counter cough syrups, which can contain anywhere from 10% to 25% alcohol as a solvent. Some prescription liquid medications also contain alcohol, though newer formulations use it less often. In each case, residual alcohol coats the mouth and throat and dissipates within roughly 15 minutes.

Dentures, Braces, and Oral Piercings

Dentures, braces, permanent retainers, and tongue piercings can trap small amounts of alcohol in crevices that saliva doesn’t rinse quickly. If you’ve had a drink and then take a breath test, these devices can hold the alcohol longer than it would otherwise linger, releasing it gradually as you exhale. Courts have generally treated the presence of dental devices as a factor affecting the weight of the evidence rather than something that automatically invalidates a result.

Medical Conditions and Ketones

You’ll see plenty of claims online that diabetes and low-carb diets routinely trigger breathalyzers. The research tells a more nuanced story.

Diabetic Ketoacidosis

In uncontrolled diabetes, the body breaks down fat for energy and produces ketone bodies, including acetone. Acetone gives the breath a fruity smell that is sometimes compared to alcohol.² Whether a breathalyzer confuses it for ethanol depends on the sensor.

A study testing two common breath alcohol detection methods, an Alcotest device and a fuel cell electrode, along with three blood-testing methods, found no cross-reaction with ketone bodies in nine severely ketotic diabetic patients.³ A Department of Transportation evaluation confirmed that fuel cell breathalyzers are “in practice, specific for alcohol” because the voltage they use prevents the oxidation of acetone.⁴ The devices most vulnerable to acetone interference are semiconductor (Taguchi) sensors, which show up in cheap personal breathalyzers, not in the evidential instruments used at police stations.

Ketogenic Diets

Low-carb and ketogenic diets put the body into nutritional ketosis, which produces acetone on the breath by the same mechanism, just at a much lower intensity. Since even the much higher acetone levels in full-blown ketoacidosis didn’t trigger false positives on fuel cell or properly calibrated infrared instruments, nutritional ketosis from dieting poses less of a practical risk. A cheap semiconductor-based personal breathalyzer might show a small reading. A law enforcement evidential instrument is unlikely to.

GERD and Acid Reflux

The theory sounds plausible: acid reflux pushes stomach contents, potentially including alcohol, up into the esophagus and mouth where the breathalyzer picks it up. The evidence doesn’t really support it. Researchers studied ten patients with severe GERD, gave them alcohol, and tried to provoke reflux using an abdominal compression belt. Even when four of the ten subjects experienced confirmed gastric reflux during the study, the breath readings did not deviate significantly from blood alcohol levels. The researchers concluded that the risk of stomach alcohol erupting into the mouth and falsely raising an evidential breath test result was “highly improbable.”⁵

GERD remains a common defense argument in DUI cases, and a particularly severe episode at the wrong moment isn’t impossible. The controlled research suggests this scenario is far less likely than it is often made to sound.

Asthma Inhalers

This one is real, but temporary. Spanish researchers tested multiple asthma inhalers and found that all of them produced positive breath alcohol readings in the first few minutes after use, with most readings above Spain’s legal limit.⁶ A follow-up study confirmed the findings and added a useful detail: every reading returned to zero within ten minutes of use.⁷ Patients who used a spacer device or took lower doses produced smaller readings.

The researchers tested inhalers both with and without alcohol as a vehicle and found no significant difference between the two groups. The false positive appeared to come from the propellant gases rather than the alcohol content itself.⁶ Modern inhalers have moved away from chlorofluorocarbon propellants, but hydrofluoroalkane propellants can still interfere in the first few minutes after use.

Food and Beverages

Commercially sold kombucha must contain less than 0.5% alcohol by volume to be classified as a non-alcoholic beverage. Drinking it could create a slightly elevated reading immediately afterward, but getting anywhere near the legal limit would be very difficult. The trace alcohol dissipates from the mouth quickly and doesn’t accumulate meaningfully in the blood at those concentrations.

Other fermented foods such as certain breads, very ripe fruit, and fermented sauces contain even smaller amounts of alcohol. They might briefly register on a sensitive device immediately after eating, but the amounts are trivial. Energy drinks, despite their reputation, generally don’t contain alcohol and aren’t a realistic source of false readings.

Environmental Chemicals and Solvents

Paint fumes, adhesives, cleaning products, and industrial solvents contain volatile organic compounds that some breathalyzer types can’t fully distinguish from ethanol. The concern is most relevant for workers in auto body shops, manufacturing plants, and similar environments. The practical risk is low. Research evaluating whether occupational exposure to paint solvents could register on an Intoxilyzer 5000 (a widely used evidential instrument) found no empirical evidence that solvents from paint products are retained in the lungs long enough to produce a false reading. Solvents dissipate quickly from the lungs, and the standard observation period provides additional protection.

One exception: someone who has literally rinsed their mouth with a solvent, as in a workplace accident, could produce a short-lived reading from mouth contamination, much like the mouthwash effect. Waiting 15 minutes eliminates that interference.

Why the Type of Breathalyzer Matters

Not all breathalyzers work the same way, and the sensor type determines which substances can cause false readings. The cheap device you can buy online and the machine at the police station are different instruments.

Fuel Cell (Electrochemical) Sensors

Fuel cell sensors oxidize ethanol at a specific voltage, producing an electrical current proportional to alcohol concentration. The voltage is set to prevent the oxidation of acetone and most other interferents.⁴ Carbon monoxide and some tobacco smoke compounds can create minor interference, but the observation period handles that. Most law enforcement agencies use fuel cell sensors, and in real-world conditions they are effectively specific for ethanol.

Infrared Sensors

Infrared instruments measure how breath absorbs light at specific wavelengths. Ethanol absorbs infrared light in a characteristic pattern, but acetone and some other organic compounds absorb in overlapping regions. Modern dual-wavelength infrared instruments distinguish ethanol from acetone by comparing absorption at two wavelengths. Older single-wavelength models were more susceptible to interference, though even those showed no problematic responses to acetone at concentrations below 350 micrograms per liter.⁸

Semiconductor (Taguchi) Sensors

Semiconductor sensors are what you’ll find in inexpensive personal breathalyzers that sell for $20 to $50. A heated tin oxide surface reacts with combustible gases, but it can’t reliably separate ethanol from acetone or other volatile compounds.⁴ The DOT evaluation found these sensors significantly sensitive to acetone at higher concentrations. If you’ve ever gotten a puzzling reading on a personal breathalyzer after a few days on a low-carb diet, this is probably why. Law enforcement agencies don’t use semiconductor sensors for evidential testing.

Mouth Alcohol Safeguards on Evidential Machines

Modern evidential breathalyzers also run slope detection algorithms that monitor the alcohol concentration profile as you exhale. If the pattern looks unusual, such as a rapid spike followed by a decline (the signature of mouth alcohol rather than deep lung air), the machine flags the sample. Some instruments also compare the ratio of ethanol to carbon dioxide or water in the breath, flagging results where the ethanol proportion is suspiciously high. Fuel cell instruments can use dual sensors that measure breath at slightly different times, rejecting samples where the two readings diverge beyond an acceptable threshold.⁹

The Observation Period Catches Most of This

Here is the detail that changes the calculus on almost everything above. Before administering an evidential breath test, officers are required to observe you for a waiting period, typically 15 to 20 minutes. You can’t eat, drink, smoke, belch, or put anything in your mouth. The officer watches for vomiting or visible signs of reflux.

The observation period exists specifically to let mouth alcohol dissipate. And it works. Mouthwash readings fall to zero within 10 to 15 minutes.¹ Asthma inhaler interference disappears within 10 minutes.⁷ Solvent fumes clear the lungs quickly. By the time you blow into the evidential machine, most substances on the false-positive worry list have already left your breath.

That’s also why roadside preliminary breath tests (PBTs) and evidential tests at the station often produce different numbers. Roadside devices are less precise, often use less sophisticated sensors, and may not follow a full observation period. Research comparing the two found that roadside PBTs had significantly greater variability than station-based evidential tests.¹⁰ In many states, PBT results aren’t admissible as evidence of your exact BAC at trial; they’re used to establish probable cause for arrest.

If the officer skips the observation period, runs it improperly, or administers the test immediately after you’ve used an inhaler or mouthwash, that’s a legitimate basis to challenge the result. Defense attorneys regularly argue that an inadequate observation period invalidates the test.

What To Do If You Think a Reading Was Wrong

If you genuinely believe a non-alcoholic substance or medical condition affected your breath test, a few steps strengthen your position.

Tell the officer immediately. Mention any mouthwash, inhaler use, medication, or medical condition before or right after the test. That creates a contemporaneous record. Don’t argue or refuse the test; just state the facts calmly.
Ask about independent testing. In most states, you can’t choose which test the officer administers, but many states allow you to request an independent blood test at your own expense after completing the officer’s test. Blood tests directly measure alcohol in your bloodstream and aren’t affected by mouth alcohol, acetone, or inhaler propellants.
Document everything afterward. Write down what you ate, drank, and used (mouthwash, inhaler, medication) and when. Note the timing of the test, whether an observation period was conducted, and how long it lasted. If you have a condition like diabetes, get documentation from your doctor as soon as you can.
Talk to a lawyer before your court date. Challenging a breath test result requires specific technical knowledge about the device used, calibration records, the officer’s training, and whether protocols were followed. An attorney experienced in DUI defense will know which challenges are viable in your jurisdiction and which ones courts routinely reject.

The gap between what can theoretically affect a breathalyzer and what actually produces a wrongful conviction is wide. Modern instruments, proper observation periods, and duplicate testing protocols catch most interferences before they become a problem. Where they fail is when corners get cut: a rushed observation period, a machine overdue for calibration, or an officer who doesn’t notice you just used an inhaler. Those procedural breakdowns are where successful challenges to breath test results almost always begin.

1
PubMed. Breath Alcohol Values Following Mouthwash Use
2
PubMed. Early Detection of Diabetic Ketoacidosis by Breathalyzer in a Sailor Reporting for Duty
3
PubMed. Ketone Bodies Do Not Give Falsely Positive Alcohol Tests
4
Department of Transportation. Breath Alcohol Testing – Possible Interfering Substances
5
National Center for Biotechnology Information. Reliability of Breath-Alcohol Analysis in Individuals With Gastroesophageal Reflux Disease
6
PubMed Central. Using Asthma Inhalers Can Give False Positive Results in Breath Tests
7
PubMed. Influence of Asthma Inhalers on a Breath Alcohol Test
8
PubMed. Response of Breath-Alcohol Analyzers to Acetone – Further Studies
9
PubMed Central. Mouth Alcohol and Slope Detection in Breath Alcohol Analysis
10
PubMed. Comparison of Roadside and Subsequent Evidential Breath Alcohol Results