When you’re sick, it’s written all over your face. That’s the conclusion of a new study in the Proceedings of the Royal Society B, which finds that sick people share facial features—pale skin, swollen faces, droopy eyelids, and looking tired—that reveal they might be contagious. Although those signs may seem obvious, no one has explicitly tested them until now. Researchers took mug shots of 16 Caucasian volunteers a few hours after injecting them with a placebo or a piece of bacteria that made people feel sick and caused their immune systems to respond as if they had an infection. They then showed the photos to 62 people, who rated the faces (pictured above as composite images with noninfected individuals on the left and infected on the right) as “sick” or “healthy” in 5 seconds or less. Raters identified 81% of sick people better than chance. But, what is it about our faces that give away whether we’re feeling under the weather? To find this out, a separate group of 60 people assessed how sick and tired the people in the photos looked and the extent to which each trait—pale skin and lips, droopy eyelids and corners of the mouth, how puffy their faces looked, eye redness, and tiredness—publicized illness. The researchers found pale skin and hanging eyelids were the best predictors of sickness. So, if staying healthy is part of your New Year’s resolution, perhaps give pallid and tired looking friends and colleagues a wide berth.