Can Mouthwash Trigger a Positive Breathalyser Test?

Can mouthwash really cause a positive breathalyser test? Learn how alcohol-based mouthwash may affect your reading, and with Spain’s new alcohol limits coming, discover what precautions drivers should take to avoid fines.

For years, there’s been debate over how certain products, like mouthwash, might affect breathalyser tests.

On top of this, the Guardia Civil has acknowledged the possibility of false positives caused by alcohol-based mouthwash. While the alcohol in mouthwash is not consumed, it can sometimes remain in the mouth and be picked up by a breathalyser. However, studies show that this effect typically lasts for only 10 to 15 minutes​.

With the potential new alcohol limits on the horizon, it’s important to understand exactly how the Guardia Civil administers breathalysers.

Guardia Civil Procedures

In Spain, the Guardia Civil uses two types of breathalysers. The first is a mobile device used during roadside stops, which gives an initial reading. If the result is positive, a more accurate, evidential breathalyser is used to confirm the result. There is a waiting period between the first and second tests, which would normally allow alcohol from mouthwash to dissipate.

So, beware, if you’ve just rinsed with an alcohol-based mouthwash before hitting the road, that fresh minty breath could still catch you out with a false positive.

Learn about the breathalyser and how it works in Spain.

Stay tuned for more updates.