The Five-Second Rule -- Does It Work?


Sothat last bite of a tasty morsel just dropped to the floor. The five-secondrule says if we're quick about it, we can still pop it in the mouth and enjoyit.

A few years ago, research disagreed. In a 2007study, crops of Salmonella, the bacteria that causes fits of diarrhea, wereplaced on wood, tile and carpet. Pieces of bologna were then dropped on thesurfaces for 5, 30 and 60 seconds. On the wood and tile surfaces, 99 percent ofthe bacteria were transferred nearly immediately. Same results occurred withthe carpet, though a smaller amount of bacteria were transferred. With awarning that as few as 10 salmonella bacteria can cause gastroenteritis,doctors warned that the five-second rule should be trashed.

Butsometimes research just doesn't add up. Kids throw all kinds of things in theirmouths, and rarely do we see it result in illness. In fact, developed countriescarry a reputation for being too clean. Associated with this cleanliness arethe increased incidence of hay fever, eczema, and more serious diseases such asasthma, inflammatory bowel disease, multiple sclerosis and type I diabetes. Soshould playing in the dirt be banned, or do we welcome it?

Thehygiene hypothesis offers a possible answer. It suggests that if we stay toosanitized, we can't ward off some diseases. Here's the reasoning. Our immunesystem kicks in without our knowing it whenever we ingest, inhale or touch asubstance that represents foreign material to our bodies. That's called anantigen. The body fires up in response to these antigens, making a variety ofcells and antibodies. Sometimes it triggers an allergic response (we sneeze,itch, or develop a rash), and sometimes we become desensitized to the antigenand it doesn't ever bother us again. We just don't know what triggers what.

Lotsof things can be innocuous antigens, but often its bacteria and viruses. Beingaround dirt exposes us to more antigens. If we tolerate it as kids, we build upa response to those dirty antigens and we're all the healthier for it. That'sthe yet unproven hygiene hypothesis.

Wemay be closer to how it all works. A recent researchstudy looked at what parents do to clean off a dropped infant pacifier.Turns out moms who gave it a quick wash in their own mouths left a bundle ofnew bacteria on the sucker. When it went back into little Billy, it exposed himto a new crowd of organisms. Gross, maybe. But those same kids enjoying thelicked-clean pacifiers were less likely to get eczema and asthma later as kids.

Somaybe we can combine the five-second rule with the hygiene hypothesis and add adose of common sense. Do all we can to avoid Salmonella, check. Playing in thedirt? The more the merrier. And licking the pacifier? Let's leave that up tomom.

Courtesy: University of Nebraska Medical Center