https://www.wired.com/story/cant-stop-touching-your-face-science-has-some-theories-why/

By now the message should be clear: Your hands are not your friends. Public health officials have told us repeatedly that putting your fingers near your eyes and mouth offers easy access to the new coronavirus. But they know it isn’t easy to follow this advice. (They can’t even follow it themselves.) One small study found that medical students, who really must know better, touched their faces an average of 23 times per hour during a lecture, or once every 2.5 seconds. This finding, like many others one can find in medical journals, makes a simple and prescriptive point: It tells us that we’re all a bunch of dirty self-inoculators, in the hopes of getting us to stop. But there’s another body of research into this same behavior, and one that tries to touch on deeper questions of its origins: Could there be an evolutionary basis among human beings (and our kindred species) for this unhygienic quirk? Might the rubbing of one’s face with germy digits come from primal urges that blossomed on our branch of the tree of life?

We do know it’s likely you’ve been pawing at your face since before you were even born. The well-established fact that fetuses will, in utero, touch their fetal hands to fetal faces, has led to scientific inquiry. One recent study conducted ultrasounds on 15 women from week 24 to week 36 of their pregnancies and found that fetuses were more likely to touch their faces with their left hands when the women reported feeling stressed. The same researchers published another small study hinting that the fetuses of women who smoke cigarettes might be more likely to touch their faces than those of nonsmoking women, although that finding was not statistically significant.