Can you tell someone is sick just by looking at them?

When you’re sick, you may feel like everyone around you can tell.

Between your red, runny nose and teary eyes, it might seem like your face is a dead giveaway of how you’re feeling. And according to recent research, we really may be able to tell an individual is sick just by looking at them.

For the study, 22 participants were given an injection – some received bacteria while others were given a placebo (note: the injections didn’t make participants sick but led to an inflammatory response because it “tricked” their immune systems.)

A couple of hours after the injections, the participants each had a headshot taken. They wore no makeup and made no facial expression for a more even comparison. For a second part of the study, each participant who received the bacteria injection the first time was then given the placebo, and those who received the placebo the first time received the bacteria injection. They were then photographed again.

A different group of more than 60 participants were then shown the first set of photos – each for five seconds – and were asked to determine if the individual in a picture appeared sick or healthy. They received an accuracy score of .62 (.5 was complete randomness and 1.0 was perfect identification.)

Those in the photos who were given the bacteria injection were rated by participants as appearing to have paler features, redder eyes, a more tired expression and a more swollen face than those who were given the placebo injection.

Dr. Amrinder Singh, family medicine physician with Advocate Medical Group, says the research is interesting, as it focuses on the ability to judge based on human instincts.

“This is made more compelling as health care is constantly improving with technology, especially artificial intelligence,” he says. “The real question will be whether bias will be involved in sensing whether a patient is truly sick. It also looks further into the concept that we as humans have more ability to understand each other than previously thought.”