Can Mouthwash Affect a Breathalyzer Test?
It’s a question many people are surprised to learn has some scientific basis behind it: can mouthwash affect a breathalyzer test?
The short answer is yes; certain types of mouthwash can temporarily influence a breath test result under specific circumstances. However, that does not automatically mean someone will be wrongly convicted of DUI because they used mouthwash before driving.
Understanding how breath testing works can help explain why this issue sometimes comes up in DUI cases.
Why Some Mouthwashes Matter
Many mouthwashes contain alcohol as an ingredient. In fact, some over-the-counter mouth rinses have relatively high alcohol content.
When a person uses an alcohol-based mouthwash shortly before taking a breath test, residual alcohol can remain in the mouth for a short period of time. This is often referred to as “mouth alcohol.”
Because breath testing devices are designed to detect alcohol, the presence of residual mouth alcohol can sometimes affect the reading if testing occurs too soon afterward.
How Breathalyzers Measure Alcohol
Breath testing devices are intended to estimate blood alcohol concentration (BAC) by measuring alcohol deep in the lungs, known as alveolar air.
However, if alcohol is still present in the mouth from:
- Mouthwash
- Recent drinking
- Burping or regurgitation
- Certain dental products or medications
…the machine may temporarily detect alcohol that is not actually coming from the bloodstream.
This is one reason DUI testing procedures include safeguards designed to reduce inaccurate readings.
The Importance of the Observation Period
California DUI testing procedures generally require an observation period before administering a breath test.
During this period, officers are supposed to monitor the person to ensure they do not:
- Eat or drink
- Smoke
- Vomit or regurgitate
- Place anything in their mouth
The purpose of this waiting period is to help ensure that residual mouth alcohol dissipates before testing occurs.
If proper procedures are not followed, questions may arise about whether the breath test result was reliable.
Can Mouthwash Cause a False High Reading?
In some situations, alcohol-based mouthwash may temporarily elevate a breath test reading immediately after use. However, the effect is usually short-lived.
A properly conducted observation period is generally intended to eliminate this issue before testing occurs.
That said, if the test was administered too quickly after mouthwash use, it could potentially become a factor worth examining in a DUI case, especially if the BAC result was close to the legal limit.
Does This Mean a DUI Case Automatically Gets Dismissed?
The fact that someone used mouthwash does not automatically invalidate a breath test or lead to dismissal of DUI charges.
Instead, it becomes one possible factor among many that may affect how reliable the testing process was. The significance of the issue depends heavily on:
- The timing of the mouthwash use
- Whether proper observation procedures were followed
- The actual BAC result
- Other evidence in the case
If there are concerns about testing accuracy, those concerns may become part of a broader defense strategy.
Other Things Besides Mouthwash Can Affect Breath Tests
Mouthwash is not the only thing that can potentially influence a breathalyzer result.
Other possible factors may include:
- Acid reflux or GERD
- Certain medications
- Dental work or oral injuries
- Improper machine calibration or maintenance
Breath testing is a scientific process, and like any testing method, it depends on proper procedures and functioning equipment.
Why Low BAC Cases Often Receive More Scrutiny
Issues involving mouth alcohol tend to become more important when a breath test result is close to the legal limit.
For example, if someone tests barely over 0.08%, even a small testing issue may become more significant than it would in a case involving a much higher BAC reading.
In these situations, defense attorneys often closely examine:
- The timing of the test
- Officer procedures
- Maintenance records for the device
- Any possible sources of contamination or interference
Breath Test Evidence Can Be Challenged
Many people assume breathalyzer results are automatically accurate and impossible to dispute. In reality, breath testing evidence can sometimes be challenged depending on how the test was conducted and whether proper protocols were followed.
That does not mean every breath test is flawed, but it does mean the details matter.
A DUI defense attorney can review whether:
- Proper procedures were followed
- The machine was functioning correctly
- External factors may have affected the result
Speak With a DUI Lawyer
If you were arrested for DUI and believe mouthwash or another factor may have affected your breath test result, it’s important to have the evidence carefully reviewed.
San Diego DUI defense attorney Rick Mueller has extensive experience analyzing DUI breath testing procedures and identifying potential issues with chemical test evidence.
Every DUI case is different, and even small details can matter when it comes to challenging the reliability of a breath test. An experienced attorney can help you understand your options and evaluate the strength of the evidence against you.
Can Mouthwash Affect a Breathalyzer Test?