Hey, Matt:

I was using one of those hand sanitizers the other day and noticed on the bottle: “kills 99.9% of all germs.” What about the .1% that they don’t kill? Let’s say there are roughly 100,000 different germs out there. If the hand sanitizer kills 99.9% of them, it would mean there’s at least 1000 germs that could wreak havoc on my otherwise sanitary hands. Should I lose a little bit of sleep over this or get some therapy?

— SLH, via email

Hey, Matt:

Okay, we have a hygiene debate going on. Young girls saying they don’t “wash their bottoms” because it’s creepy to put their hands there, versus Mom’s insisting they must do a soapy hand scrub of their “privates/fannies”; shower water alone doesn’t cut it.

— Nameless, via snail mail

Communications from opposite corners of germworld. We’ve put Nameless’s letter out on the patio so it won’t contaminate anything, so I guess we’re set to go.

Every time you stare at your cube and wonder how you ended up in such a tedious place, consider some researchers at the University of Georgia who decided it would be a really good idea to figure out how many bacteria there are on Earth. Counting bacteria has to beat anything you’re up against. But, hey, they survived it and came up with a number: 5 followed by 30 zeroes. That’s five nonillion. Lucky for us, most of these are deep in the soil and under water. Some even live 40 miles out in the atmosphere. Bacteria in and on humans and animals make up only 1% of the total. But in that 1% are some true nasties.

I don’t know whether this will send SLH to bed or to the shrink, but I think we have to clarify what the hand-sanitizer people mean when they say it “kills 99.99% of germs.” They mean that in their product tests, their sanitizer killed 99.99% of the germs that happened to be on the test subject’s hands, not 99.99% of all possible germs in the world.

If you want to try this at home, first get your hands germy. One scientifically acceptable method of doing this is to scrabble your hands around in your hair for a while. (I’m not kidding.) Then you get two petri dishes that you should be storing in the kitchen for just such an opportunity and stick your fingers down on the first one. Then you squirt a little sanitizer on your hands and squish that around for 15 seconds. Then stick those same fingers down on the second petri dish. Hold the dishes at just the proper temp for a day or so, then look at the results. Dish one should be loaded with finger-shaped piles of bacteria and viruses. Dish two might have a tiny bit of growth. That’s how you get the 99.99%. In dish one, odds are you’ll be cultivating a heap o’ staph. And E. coli. Can’t forget our friend E. coli.

To help SLH towel off and relax a little, here are some infobits on hand sanitizers. Most of them work just fine, as long as they have enough ethanol or isopropanol in them. The CDC says you need to find a sanitizer that is at least 60% alcohol. These will kill germs on contact, but they don’t continue to kill germs one or two hours out.

One oddity that was found in the testing of sanitizers is that they worked great on gastrointestinal bugs but not on things like rhinovirus and other respiratory-related germs and viruses. Since the alcohol should have killed these, scientists figure the problem was with the test subjects. A person is much more likely to use a sanitizer after dealing with some toilet-related event than after a sneeze. Ergo, sneeze bugs remained on their hands. Sanitizers don’t clean off any kind of dirt or nose goop that you get on your hands. You need to use soap and water to remove the grody stuff, then use the sanitizer. And BTW, testing has also found that antibacterial soaps are no better than regular soaps. They don’t do much sanitizing at all.

To round this all up, scientists consider our hands the biggest spreaders of bacteria. (A handshake should be followed immediately by a thorough hand-washing.) Some researchers at the University of Virginia poked around people’s houses and found the nastiest places to be the TV remote, refrigerator-door handle, doorknobs, light switches, phones, salt and pepper shakers, and kids’ toys. It’s a minefield out there.

The Virginians might have included Nameless’s young girls in their sample. They must be magical bacterial gardens by now. My suggestion to Mom is that she buy each girl her own washcloth. Maybe this terry-cloth barrier will encourage young girls to wash the icky places. (Have young girls noticed their friends backing away from them lately? Keeping a healthy distance between themselves and young girls? Moving to another desk in math class? Can young girls take a hint? Perhaps they stink.)