Germs seem to have moved toward the top of the national worry list. Millions buy antibacterial soaps and cleansers, air purifiers, and even face masks. Some people wonder if it’s safe to share a telephone, headrest, yoga mat, or exercise equipment, ride in a plane or bus, or touch an ATM machine. Feeding these concerns are a lot of busy marketers. Ads portray a dangerous world, seething with microbes. Companies that make disinfectants warn you that germs will move into your new home faster than you can. Toy companies impregnate products with germ-fighting chemicals. You can buy antibacterial cloths, towels, sheets, and mops equipped for germ warfare.

Bacteria, viruses, and other pathogens can sicken and even kill people, of course. Yet when it comes to fighting germs at home or on your person, keep a cool head. “Germs,” meaning microorganisms, are everywhere on earth and, in fact, in and on us. Trillions of bacteria reside on our skin and in our mouths, noses, intestines, and elsewhere—resident flora, as they are called. Ordinarily, they are not a problem, or can be kept at bay by basic hygiene. Some, like intestinal flora, even perform vital functions—preventing pathogens from “colonizing” the digestive tract, for instance. Exposure to microbes is actually necessary for the development of a mature immune system.

Still other types of microbes, called transient flora, can indeed be classified as contaminants, but they are usually not troublesome either. Their life span on the skin is brief, and healthy immune systems deal with them efficiently. Microorganisms are natural inhabitants of our habitat—or we of theirs (they got here first). An infant meets bacteria in its mother’s birth canal before it even begins to breathe the air. Microbes are our lifelong companions, for better or worse. Humans could not survive for long in a germfree environment.

There are many ways to defend yourself against harmful microorganisms. A healthy immune system is the best defense. A public health system that ensures safe drinking water and proper disposal of sewage is another. Clean habits are still another: keeping the kitchen and bathroom clean, washing clothes, bathing or showering at reasonable intervals, brushing and flossing teeth to remove decay-causing bacteria.

Here are answers to some questions you may have about germs.

What’s the single most important way to prevent the transmission of infectious organisms?
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 hands grimy. Covering your mouth and nose when you cough or sneeze is another important preventive.

How should you wash your hands?
Thoroughly, with soap and water. Any kind of soap is fine. Warm water cuts through oil on your hands faster, but cold water will also do the job. Rub your hands with soap and water for at least 15 seconds to loosen germs and dirt, rinse all soap away, then dry well. Soap and water don’t actually kill microorganisms, but they create a slippery environment so that the critters slide off.

Are antiseptic and antibacterial products better?
Not under normal household circumstances. Soaps with triclosan and other antiseptics do kill or inhibit bacteria, but the result is essentially the same as with regular soap. Studies have found no additional benefit from using these products. Besides being overkill, they are more likely to cause skin irritations than plain soap. The widespread use of antibacterial products may also encourage the development of drug-resistant bacteria. The only place where antiseptic/antibacterial cleaners are advised is in a hospital or similar setting.

Should you use antibacterial sponges and cleansers in the kitchen?
They aren’t necessary. Nothing can take the place of cleanliness—frequent washing of kitchen counters and utensils, particularly any that have come in contact with raw meat, and washing and/or replacing sponges and dishcloths often. An antibacterial sponge will not disinfect a countertop, and the sponge will eventually get dirty. Plain soap or detergent is just as effective in the kitchen as an antibacterial product.

Is it okay to use alcohol hand sanitizers?
When you don’t have access to a sink, alcohol gels and wipes are convenient. The alcohol kills most bacteria and viruses, but unlike antibacterial soaps, it can’t promote resistant bacteria. However, alcohol is very drying to the skin, and washing with plain soap and water is just as effective at getting rid of germs. If you do use one of these gels, make sure it contains at least 60% alcohol; less is not effective.

What about antibacterial toys, mops, phone-guards, etc.?
There’s no evidence that household products impregnated with antibacterial chemicals reduce the risk of infections. The EPA has ordered some marketers of such products to stop making misleading claims about health benefits. The danger is that if people imagine that products are “self-sanitizing,” they’ll dispense with regular hygiene—that is, soap and water—to prevent the transmission of germs.

What about anti-germ devices for use in planes?
You don’t need them. There is an increased risk of catching a cold when flying. People often blame this on poor ventilation, especially the recirculation of cabin air, but studies have found that the infection rate is the same in planes that use 100% fresh air for ventilation and those that use recirculated cabin air (which is filtered). Simple human proximity is the real culprit. If you get sick after a plane trip, it’s usually because you sat within a few feet of someone who was sneezing or coughing, or you touched an object that a sick person recently handled or coughed on and then you touched your mouth or nose. Thus, frequent flyers should be frequent hand washers. Special covers for headrests, pillows, and seats in the planes, most air filters or purifiers (for the plane or home), and various anti-germ devices advertised in catalogues and on the Internet serve little or no health purpose.

How about face masks?
There’s no evidence that wearing a mask made of paper, gauze, or cotton will protect you against infections in a plane or elsewhere. These are essentially worthless, since viruses and bacteria are small enough to pass through any ordinary weave. Masks designed for hospital use, such as the N-95, are more effective, but they won’t block all viruses. Moreover, it takes training to properly fit and handle a hospital mask; if it does trap infectious organisms, you can become infected while handling it.

Do gym equipment and exercise mats spread germs?
Microbes thrive in the warm, damp environments found in many gyms, health clubs, and pools. But facilities that are properly cleaned and disinfected pose little serious risk, especially if you shower after working out, or at least wash your hands before touching food or your face. Worries about germs shouldn’t keep you from the gym.

Words to the wise: Living involves sharing space and objects with other people and with the invisible flora of the earth. We cannot—and do not need to—walk around wrapped in plastic. People with impaired or underdeveloped immunity, such as the elderly, young children, pregnant women, patients undergoing chemotherapy, and those with certain diseases (HIV infection, for instance), do need to take extra precautions because they can get sick from lower exposures and are at higher risk for dangerous complications. But a healthy immune system (including the skin) is good at protecting against most microbes. Usually all that’s needed is commonsense precautions like handwashing and not sharing intimate objects, such as toothbrushes.