How To Tell If Someone Near You Is Sick

If you think you’re about to get sick, bite your lips or grab some lipstick. Pale lips may be one of the first visible signs that someone is getting sick, according to a new paper published Tuesday. The paper by researchers at the Karolinska Institute in Sweden, found that people’s faces may change in noticeable ways as they get sick.

“We took features that we thought were going to change during sickness. Most of them changed, actually,” John Axelsson, a psychologist at Karolinska Institute, told Newsweek. Those features included red eyes, paler skin—and pale lips. In fact, pale lips appeared to be the strongest response to being sick, Axelsson said, “which we didn’t expect.”

However, pale lips were not the sign that most people used to figure out who was sick, according to the paper. “Pale lips might be a very good cue if you want to find someone who is acutely sick—someone who is sick just now,” he said. However, that may not be as reliable an indicator, due to natural variability in people’s healthy lip color. Paler skin or drooping eyelids—cues used more often to figure out who might be sick—were considered better indicators that an illness has lingered. “These cues are probably better at telling us whether someone is sick or not,” he said. 

Man sneezing A man covers his face while sneezing near one of the garden show pieces at the Chelsea Flower Show in London on May 24, 2004. JIM WATSON/AFP/Getty Images

To do the study, researchers didn’t just ask for volunteers who were sick—they made them actually feel sick. In order to figure out that we're sick, our immune systems look for stuff on the surface of viruses or bacteria or other pathogens. This "stuff" includes a kind of molecule called lipopolysaccharide, which is found on bacteria like E. coli and Salmonella. So Axelsson and his colleagues injected the participants with this lipopolysaccharide—the injection wouldn’t actually give people a disease, but it would make someone's immune system act like they had a disease for a few hours.

“It’s a quite common model to study how people behave and change their behavior when they’re sick,” he said.

However, the study has some major limitations—mostly due to who was studied. The group of participants only included 16 young, white people; that’s too small to determine if there were any differences between men and women. (That may not be important; “we think the signs are general,” Axelsson said.) But extrapolating these signs to any other groups of people isn’t possible without more research.

And it turns out we’re pretty awful at picking sick people out by faces, alone. People could guess when someone was sick about 62 percent of the time—a bit better than if they were guessing at random. 

There are a few other cues that help people figure out if people might be sick, Axelsson said, including how someone walks, behaves and even smells. With more than just a sick face to look at, he said, "I'm pretty sure you would be a lot better at judging who is sick and who is healthy."