Ask A Scientist

Does the five-second rule actually work? 

Asked by: Brady Wheeler-Nieman
School: St. John the Evangelist School / Binghamton
Grade: 5
Teacher: Mrs. Rai
Hobbies/Interests: Baseball, reading and writing
Career Interest: Writer

Answer from Douglas W. Green, EdD

Adjunct Lecturer, Binghamton University

Other: Former principal at Woodrow Wilson Elementary in Binghamton, NY
Research area: Leadership, Learning Theory and Social Media
Interests/hobbies: Playing my banjo, biking, golf and reading
Family: Daughter Lena, age 29, who works for the Teen Nickelodeon channel in Times Square, New York City.  

Unless your floor is totally disinfected, the answer is no. In case you aren't familiar with this rule, it is often invoked when somebody drops something they really want to eat on the floor. The idea is that if you pick it up fast enough, there isn't time for dirt, microbes, or toxic chemicals to attach to the food's surface. This is like thinking that if you pull a piece of tape up from a piece of paper fast enough, it somehow won't stick. 

This may not sound like a scientific subject, but it has been a topic of research. The findings are not surprising. The amount of foreign substances that stick to a piece of food will depend on the nature of the food and the contents of your floor. A dry cracker, for example, will pick up far less than a moist piece of lunch meat. Floors usually contain a greater assortment of foreign substances than other surfaces like kitchen counters. This depends on how often and how well the floor and the rest of your home is cleaned. 

So just what might stick to dropped food? There are three basic materials. First is dirt or sand particles, which are fairly nontoxic. You probably eat some most days as it is likely to be on fruits and vegetables that aren't thoroughly cleaned. Next are microbes, mainly bacteria. Some cause disease, while others do not. If you eat yogurt, you know what some bacteria taste like, as it takes bacteria to make yogurt from milk. A common bacteria that can make you sick is salmonella, which is often found in spoiled eggs. Bacteria like these are called pathogens. Various pathogens work in different ways. With some you need to digest a lot to get sick. With others, a few will do it.

The third materials that lurk on floors are toxic chemicals. To find out what they might be, just look at the labels on your floor and carpet cleaners. While there is a trend towards making non-toxic cleaners, most of what people still use contain chemicals you don't want to eat. If you have eaten dropped food in the past without getting sick, you have been lucky. My advice is that it is not worth the risk. Check this link to watch the Myth Busters do research on the five-second rule http://bit.ly/1bjGcgl.

Last Updated: 9/18/13