Five second rule

From Academic Kids

This article is about a myth regarding fallen food. There is also an article on ice dancing which has a five second rule.

The five second rule is a popular North American old wives' tale. The rule states that foods -- particularly sweet foods like cookies -- that have fallen to the ground will not contract any germs until five seconds have passed. The rule provides a convenient rationale for eating food off the floor, and is usually invoked when a group of people are present. Thus, for example, a person might drop a jelly bean, pick it up quickly, tell his friends "it's within five seconds" and then eat the candy.

It is usually safe to eat food from a relatively clean floor. However, the notion that germs from the floor will not reach food for at least five seconds is false.

The five second rule is seldom invoked in the case of sticky foods, such as ice cream, to which dirt visibly clings. The origin of the five-second rule is unknown.



A study on the five-second rule was performed by Jillian Clarke, a high school senior, during a seven-week internship at the University of Illinois in 2003. Clarke and a doctoral candidate named Meredith Agle took swab samples from various floors around campus. They then looked at the samples under a microscope and discovered that they did not contain significant amounts of bacteria. The conclusion was that in most cases, dry floors would be safe to eat from.

However, Clarke also wanted to test the five-second hypothesis in cases where the floor was known to be contaminated. She therefore spread E. Coli on both rough and smooth floor tiles in a laboratory, placed pieces of gummi bears and cookies on the tiles for various amounts of time, and then examined the foods under the microscope. All the foods had a significant amount of bacteria after less than five seconds. Her findings therefore disprove the five-second rule.

In the course of her research, Clarke also conducted a survey to sample opinion on the five-second rule. She found that seventy percent of women and fifty-six percent of men were familiar with the five-second rule, and most utilized the rule in their decisions to eat food that had fallen on the floor. She also found that women were more likely than men to use the rule, and that cookies and candy were more likely to be picked up than broccoli or cauliflower.

Clarke's work won an Ig Nobel Prize for Public Health in 2004.


The five second rule is sometimes called the three second rule, ten second rule, or the fifteen second rule, to some extent depending on the quality of the food involved or the intoxication level of the individual quoting the rule. For example, in American college dormitories the ten second rule is often quoted as the "drunk version" of the five second rule.

It is also widely believed that, in the home, the five second rule can be extended to at most 15 seconds. In public places and restaurants, however, the amount of time is generally shortened.

Related rules

There is a related justification for eating just-fallen food, where the individual will "kiss it up to God", that is, the item is literally kissed just before being eaten. Generally, this only "works" if done in the same five to fifteen second time frame.

Other occasions which call on a "five second rule" include:

  • Once a seat has been vacated for five seconds, the five second rule is said to be in effect and anybody may take that seat.
  • If a teacher is more than five minutes late to a lesson, it is believed by some students that it is acceptable to leave. Note: This is generally not accepted by teachers, although some schools have official policies that allow students to leave without penalty if an instructor is sufficiently late.
    • Add five minutes per degree if in college. For example, one waits fifteen minutes for a professor who has a Ph.D.

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