Pictured: Superbug spawner, or savior to us all? Neither!
Recently, I was sitting in a meeting and reached for the dispenser of Purell hand sanitizer sitting on the conference room table. A colleague of mine gave a small, rueful shake of her head to the person on her other side. Apparently I had erred. I asked what was the matter, and got a brief answer to the effect of “because superbugs.” We exchanged nothing more about it; the interaction was over before the alcohol had dried from my hands.
I wouldn’t have thought anything of such an interaction with anyone else, but my colleague is a PhD student in immunology, six years older and more schooled than I, doing her doctoral research in a lab run by a physician-scientist — a specialist in infectious disease, no less. A touch ironic.
And so I noticed a need for some mythbusting: alcohol-based hand sanitizers do not breed resistant bacteria. (more…)
Whipworms in the intestine. Click to enlarge.
Humans evolved in an environment where they were exposed to animals, dirt, and a variety of pathogens and parasites. Our immune systems evolved to cope with that environment. Now most of us live in a different environment, with safe drinking water, flush toilets, food inspection, immunizations, and public sanitation. This means that we are far less likely than our ancestors to die of infectious diseases or to harbor intestinal worms. But it seems that the cleaner we get, the more likely we are to suffer from allergies and autoimmune diseases. One hypothesis is that our immune systems evolved to require early challenges by parasites and pathogens in order to develop properly. A hygienic environment fails to give our immune system the exercise it needs, resulting in imbalances and malfunctions.
The hygiene hypothesis was first proposed to explain observations like these:
- Hay fever and allergies were less common in large families where children were presumably exposed to more infections through their siblings.
- Polio attack rates were higher in high socioeconomic groups than in lower ones.
- Allergies and many other diseases were less common in the developing world.
Investigation of these and other phenomena is contributing to a better understanding of the immune system, which is a good thing. At the same time, it has led some people to deliberately infect themselves with intestinal worms in an attempt to cure their allergies and autoimmune diseases, which may not be such a good thing. These treatments are far from ready for prime time, are risky, and they have a high yuck factor. The very idea of deliberately infecting yourself with worms is unpalatable, and finding wiggly live creatures in your stool or passing a 20 foot tapeworm are not generally considered to be pleasant experiences. (more…)