Judging by the number of hand sanitizer bottles carried by your average San Franciscan, we are in the midst of a war on germs. Along with stories about flesh-eating and drug-resistant bacteria, this year’s pandemic H1N1 influenza is prompting many to cover, wash, and wipe their way toward the goal of a personal sterile zone. But history teaches us that efforts at sanitation can have unintended consequences.
Prior to improvements in sewage disposal, polio infection most commonly occurred in infants. At this young age, the disease was generally mild and resulted in lifelong immunity. Then, improved hygiene resulted in polio infections occurring later in life, when severe disease and paralysis were more likely. By 1950, the highest incidence of polio-related paralysis was among five- to nine-year-olds, and an epidemic was underway.
A twenty-first century analogy is that some evidence suggests that the current mania for sterility may be adding to another epidemic: asthma.
Childhood exposure to microorganisms (“germs”) is critical to the development of a healthy immune system. So, while doorknobs, sandboxes, and snot-nosed classmates may be conduits for infection, they are also necessary for an immune system learning how to recognize and fight infection. Studies have linked increasing rates of asthma to fewer opportunities to encounter germs at a young age, an idea that has become known as “the hygiene hypothesis.” Introduced in 1989, this theory proposes that an immune system deprived of adequate exposure to germs is more likely to develop in a way that leads to a disordered immune function, such as that seen in asthma. It may be that all our efforts to avoid illness in our children are resulting in—more illness.
This is not to say that the development of systems allowing for clean drinking water and appropriate sewage disposal was a bad idea. Nor, for that matter, is hand sanitizer. Studies have shown that hand sanitizer is effective in preventing infections in health care settings and results in better compliance with hand-washing standards and less dry skin. There are even some controversial studies that suggest that using these hand rubs in schools can reduce absenteeism. So, as with many questions in medicine, the answer to the question, Are we too preoccupied with germs? is, It depends.
Rigorous, repeated hand washing or sanitizing is necessary in many settings—when someone at home is sick, or when one is working in a healthcare or food preparation setting. But apart from these situations, it’s likely better to take it down a notch. Germs are everywhere and have evolved alongside humans for millennia. Influenza pandemics, outbreaks of virulent Staph bacteria, and threats of new and dangerous viruses will always be a part of life, but there’s no need to live in a bubble. Today’s “germscape” warrants the same approach as in the past: play in the dirt, stay home when you’re sick, wash your hands (or use your rub) when it’s appropriate, and see your doctor when you feel ill.
Dr. Jordan Shlain is the founder and medical director of Current Health Medical Group (currenthealth.md). Dr. Shlain is an assistant clinical professor at the UCSF Medical Center and a medical economics lecturer at UC Berkeley.
