Dear Straight Dope: I've got little trails of ants wandering through my house as is usual in rainy weather. I don't pay much attention to them. In fact I kind of like them. Most of the time I keep food well contained, but the other day I noticed ants had gotten into a box of cookies. I was in a cookie mood so I brushed the ants off and ate one of the cookies. When I told one of my friends I had done this she freaked. She is constantly battling ants and says they are filthy and carry appalling diseases. I'll avoid eating food that ants have touched if a noted authority says I should. I appreciate any insight you can provide. Donya Wicken

Doug replies:

I have the same ants in my house (Argentine ants). Let’s put it this way: the types and numbers of bacteria on an ant aren’t significantly different from those in the air in your home–the same air that’s in contact with your cookies all day long. In fact, if there’s any difference, the ants will be cleaner, as any tendency they may have to accumulate contaminants on their feet while walking is countered by three important factors, which you can point out to your friend:

Ants groom themselves more than almost any other type of animal known. In this respect their feet are second in importance only to their antennae, which are immaculate. The physical structure of ants’ feet, and the nature of the lipid layer covering their exoskeleton, makes them a poor site for bacterial retention even if they didn’t groom themselves so well. The chemical secretions in ants’ saliva and external glands are loaded with some remarkable antimicrobial agents–ants, after all, are assaulted by infectious agents in the environment just as we are (possibly more so when they live underground). They’ve had millions more years than primates to develop the body chemistry to make their bodies and nests as close to sterile as can be conceived–imagine if human sweat were composed of Lysol and penicillin.

We’d be lucky if we were as sterile and disease-free as an ant. Ants almost never get sick compared to humans. You introduce far deadlier microbes into your body simply by using two unwashed fingers to touch your cookies than would a million ants. Houseflies may visit biohazards such as carcasses or feces and go from one such place to another without grooming in between. Not ants. Whatever is on an ant’s feet as it walks across a cookie is pretty much whatever it picked up within a six-inch radius of that cookie, so unless you store your cookies in the same cabinet as your medical waste and other biohazards, have no fear of what ants are carrying.

If your friend were truly worried about filth, and tried to meet or exceed the standards set by ants, she’d have to wear surgical gloves for the rest of her life, and pass every piece of food she ever ate over an open flame to sterilize it. In other words, it’s probably not the filth that bothers her, it’s the bugs.

Doug

Send questions to Cecil via cecil@straightdope.com.

STAFF REPORTS ARE WRITTEN BY THE STRAIGHT DOPE SCIENCE ADVISORY BOARD, CECIL'S ONLINE AUXILIARY. THOUGH THE SDSAB DOES ITS BEST, THESE COLUMNS ARE EDITED BY ED ZOTTI, NOT CECIL, SO ACCURACYWISE YOU'D BETTER KEEP YOUR FINGERS CROSSED.