The reader of MUY strictly followed the old motto that of "if you drink, don't drive." So, when the Civil Guard stopped him and gave him a breathalyzer test , he was amazed at the result: 0.02 milligrams of alcohol per liter of exhaled air. He was a teetotaler and expected an absolute zero. How was it possible?
On the one hand, it is necessary to consider the margin of error in the calibration of the device, called a breathalyzer or ethylmeter . But, in addition, there is a medical reason, which Ángel Niego, an expert in toxicology at the San Carlos Clinical Hospital in Madrid, explains: "It may be due to the fermentation processes that occur in the digestion of food from the oral cavity to the stomach. They cause alcohols to appear in minute quantities. "
But the driver can rest easy: if he has not drunk, he will never test positive – more than 0.25 milligrams per liter of exhaled air.
Are some foods more likely than others to produce these reactions? Dr. Nieto points out that, sometimes, they can occur with grapes, although, more than with a specific product, this phenomenon depends on the bacterial flora of each person.
Apart from food, there are other products, such as mouthwash or certain syrups , that can generate what is known as the "alcohol-in-mouth effect", although the false positive disappears when the test is repeated shortly afterwards. And what is totally useless is trying to fool the device with tricks like licking coffee beans or putting toothpaste before blowing.
