Every breath you take, they really may be watching you.

Your thumbprint, the pattern of lines in the iris of your eye: These are known to be more or less unique to each person, including you, or at least specific enough to be useful for unlocking your phone. But in a paper published Thursday in the journal Current Biology, researchers report that your patterns of breathing through your nose are so distinctive that it may be possible to identify you by breath alone, suggesting we have “breath prints.”

The study was conducted in 100 people who wore sensors for 24 hours, and the technique proved effective in distinguishing among individuals more than 90 percent of the time. The researchers who led the study also found that certain quirks of breath were linked to people’s scores on questionnaires about anxiety, among other traits, suggesting that breath monitoring over many hours may provide a useful window into mental states and disorders.

Most people rarely think about breathing, but for researchers who study smell, like Noam Sobel and his colleagues at the Weizmann Institute of Science in Israel, that regular cycle of in and out contains tantalizing information about the brain. Each inhalation comes with a firing of sensory neurons and other cells involved in monitoring the environment, and Dr. Sobel and Timna Soroka, a graduate student at the institute, wondered whether it would be possible to identify individuals from long-term recordings of their breathing patterns.

“We hypothesized, brains are unique, ergo breathing patterns would also be unique,” Dr. Sobel said.

Ms. Soroka developed a wearable sensor that fit on volunteers’ upper backs, with tubes running around to capture the airflow out of each nostril. The researchers found that by using software to analyze a day’s worth of sensor information, they could tell people apart.

There’s more to a cycle of breath than just inhaling and exhaling.

One person might have a very consistent pause just before each inhale. Another might pause some of the time and barely at other times. Someone might tend to exhale very quickly, or sigh more frequently than another. For many people, one nostril might have a greater flow than the other for some of the day.