Can Mouthwash Really Cause a DUI?

The Truth About False Breathalyzer Results in Illinois

Imagine this: you’re on your way home from a late dinner in downtown Chicago. You didn’t have a single drink, but earlier, you rinsed your mouth with a heavy-duty mouthwash. You’re pulled over near the Loop for a minor traffic violation. The officer smells alcohol and asks if you’ve been drinking. You say no. A breathalyzer is administered—and it shows you over the legal limit. You’re stunned. You haven’t had a drop of alcohol, but you’re now in custody for DUI.

Unfortunately, this is a real scenario that plays out more often than most people realize. In Illinois, mouthwash and breath fresheners containing high levels of alcohol can trigger false BAC (blood alcohol concentration) readings on portable breath testing devices. If you’ve been charged with DUI in Chicago under these circumstances, understanding your legal rights and getting immediate help from a DUI defense attorney could make all the difference.

The Alcohol in Mouthwash and Breath Sprays

Many over-the-counter mouthwashes contain high-proof alcohol—often ethanol—as a primary ingredient. Brands like Listerine, Scope, and store-brand antiseptic rinses may contain anywhere from 14% to 27% alcohol. Likewise, some breath sprays and fresheners use alcohol as a delivery base.

These products are not meant to be ingested, but they leave behind “residual mouth alcohol” that can linger for several minutes. When a breathalyzer test is administered shortly after using one of these products, the device can misinterpret the alcohol vapor in the mouth as alcohol from your bloodstream.

That’s because most portable breath testing devices used during traffic stops (commonly referred to as PBTs) are not equipped to distinguish between alcohol from the lungs—which reflects blood alcohol content—and alcohol in the mouth. These devices sample air from the mouth and upper airway. If alcohol lingers there due to mouthwash, it can result in a dramatically inflated BAC reading.

Illinois DUI Law and How Breath Test Readings Are Used

Under 625 ILCS 5/11-501, Illinois law prohibits driving under the influence of alcohol, drugs, or any intoxicating compound. A person is presumed legally impaired if their BAC is 0.08% or higher. However, drivers can also be charged if they are under the influence to a degree that renders them incapable of safe driving—even if their BAC is under 0.08%.

Breath test results, while often challenged, are used heavily by law enforcement to justify DUI arrests. Portable breathalyzers are typically used on the roadside and are not admissible at trial in Illinois. Still, they are commonly used to establish probable cause for arrest and later justify further testing.

After an arrest, a driver is typically asked to submit to an evidentiary breath test at the police station. These machines are more sophisticated, but even they can be influenced by mouth alcohol if proper procedures—like observing the suspect for 15–20 minutes prior to testing—are not followed.

The Risk of False Positives and Legal Implications

A false BAC reading caused by mouthwash or a breath spray is more than a technical error. It can become the foundation for criminal charges that carry serious consequences. A first-time DUI in Illinois is a Class A misdemeanor, punishable by:

• Up to 364 days in jail
• A fine of up to $2,500
• Mandatory alcohol education or treatment
• Driver’s license suspension of six months to one year
• Permanent criminal record (unless supervision is granted)

These penalties increase significantly if there are aggravating factors like prior DUI convictions, a child in the vehicle, or property damage. And once you’ve been charged, the burden is on you and your attorney to prove that the test result may not have been accurate.

How a DUI Attorney Can Challenge False BAC Results

If you believe your breath test was influenced by mouthwash or breath freshener, you should not try to explain your way out of it alone. Officers rarely reverse course based on your explanations. Instead, your best defense is hiring an experienced DUI lawyer who knows how to challenge flawed evidence in court.

Your attorney can investigate:

• Whether the officer asked about or noted the use of mouthwash
• The timing between the mouthwash use and the breath test
• Whether a 15-minute observation period was followed prior to testing
• Whether the testing device was properly calibrated
• Any inconsistencies between the test results and your physical behavior

In many cases, scientific evidence or testimony can show that the breath test results were likely contaminated by mouth alcohol. This can create enough reasonable doubt to win at trial—or convince prosecutors to reduce or dismiss the charges.

Can You Still Be Convicted If You Weren’t Actually Drunk?

This is one of the most frustrating parts of DUI law in Illinois. Even if you were completely sober, if the police believe you were impaired based on a faulty test and their observations, you can still be prosecuted. While a BAC above 0.08% creates a legal presumption of impairment, prosecutors are also allowed to argue that a person was “under the influence” without using that threshold.

That’s why every piece of evidence must be reviewed and challenged—starting with the legitimacy of the breath test result. In some cases, the test result can be suppressed entirely, making it much harder for the state to move forward.

Summary Suspensions: Another Hidden Threat

Even if you’re not convicted of DUI, refusing or failing a breath test (including a false positive) can result in a statutory summary suspension of your driver’s license under 625 ILCS 5/11-501.1. This suspension is automatic and takes effect 46 days after your arrest unless challenged.

For a first-time test failure, the suspension is 6 months. For refusal, it’s 12 months. These penalties are enforced by the Illinois Secretary of State, separate from the criminal case. Your lawyer can file a petition to rescind this suspension—but the deadline is short, and hearings must be requested quickly.

Protecting Your Record and Future

A DUI arrest caused by a false BAC reading can still leave you with a criminal record, suspended license, and lasting consequences for employment, insurance, and more. That’s why early legal intervention is essential. The sooner you hire an attorney, the more opportunities there are to challenge the test, suppress bad evidence, and keep the case off your record.

Don’t assume the system will fix itself. Judges and prosecutors will not automatically assume the test was wrong just because you say you didn’t drink. The defense must be built carefully, using legal motions, scientific data, and strategic courtroom advocacy.

Call Now – The Law Offices of David L. Freidberg Is Ready to Help

If you were arrested in Chicago for DUI, protect your future by contacting The Law Offices of David L. Freidberg. We have decades of experience handling DUI cases in Illinois. Our firm is available 24/7 to provide the legal defense you deserve.

Contact us today at (312) 560-7100 or toll-free at (800) 803-1442 for a free consultation. We’re available 24/7 to serve clients throughout Illinois, Cook County, DuPage County, Will County, and Lake County.