Knowing that we're in the cold and flu season, I picked up a recent issue of the University of California, Berkeley Wellness Letter to get up to speed on how we can prevent illness in our homes and offices this winter.

In that issue, a reader asked, "What's the single most important way to prevent illness?" The answer: Wash your hands often, before eating; before and after handling food, particularly raw meat or fish; after having sex; before putting in contact lenses or treating a wound; after using the toilet; after sneezing, coughing or blowing your nose, particularly when you have a cold; after changing a diaper; after playing with a pet or cleaning a litter box; and after gardening or any other task that leaves the hands grimy. That just about covers it all.

Germs are everywhere. In fact, Berkeley people often refer to them as "resident flora." And nowhere are harmful germs passed around faster than in a school classroom. I picked that up from Miss Dare, one of my elementary school teachers. Nowadays, I'm sure we'd call her a clean freak; back then, we thought of her as a walking bar of Lifebuoy soap. Remember that? With such a distinctive fragrance, there was no doubt in our 10-year-old minds that the woman not only bathed with Lifebuoy several times a day but also used it for perfume. I'm sure she had a bar with her at all times and used it frequently to maintain her impeccable personal hygiene. This teacher squeaked when she walked, that's how clean she was.

When asked how we should wash our hands, the folks at Berkeley Wellness say we should do it thoroughly with soap and water. And any kind of soap is fine. And while warm water cuts through oil on our hands faster, cold water will also do the job.

Rub your hands with soap and water for at least 20 seconds (or long enough to sing "Happy Birthday" twice) to loosen germs and dirt. Rinse all soap away, and then dry well. Soap and water don't actually kill microorganisms, but they create a slippery environment so that the critters slide off.

Drying your hands reduces bacteria levels further, but it's debatable whether using paper towels, cloth towels or a warm-air dryer is best. A study from the Mayo Clinic in 2000 found no differences between these methods in terms of removing bacteria from hands. Other research suggests paper towels are more effective. If you use a dryer, keeping your hands still removes more bacteria than rubbing them together.

There are many health reasons to wash your hands, but it can also have psychological effects. Using a variety of tests, researchers have found that hand-washing can indeed have a psychologically cleansing effect.

Hand-washing is not likely to wash away remorse over extreme misdeeds — guilt-ridden Lady McBeth for example, feverishly scoured an imagined bloodstain on her hands to no avail. Next time you feel guilty over, say, eating too many cookies or yelling at your kids, besides resolving to do better next time, see whether a good scrub helps.

Mary invites questions, comments and tips at mary@everydaycheapskate.com, or c/o Everyday Cheapskate, 12340 Seal Beach Blvd., Suite B-416, Seal Beach, CA 90740. This column will answer questions of general interest, but letters cannot be answered individually. Mary Hunt is the founder of www.DebtProofLiving.com, a personal finance member website and the author of "Debt-Proof Living," released in 2014. To find out more about Mary and read her past columns, please visit the Creators Syndicate webpage at www.creators.com.