Over at CommonHealth, Aayesha rounds up the literature on the limits of hand sanitizers, but fails to mention the collateral damage to the skin microbiome. Alcohol-based hand sanitizers kill many bacteria, viruses and fungi, but they don’t selectively target pathogens. They kill a wide swath of the microbial life on your hands, including little-understood non-pathogenic species. For an ecological analogy, think of using Agent Orange to kill a couple weeds.
A good introduction to the skin microbiome is a recent article in Nature Reviews Microbiology by Elizabeth A. Grice and Julia A. Segre (9, 244-253 (Apr. 2011)). From the abstract:
The skin is the human body’s largest organ, colonized by a diverse milieu of microorganisms, most of which are harmless or even beneficial to their host. Colonization is driven by the ecology of the skin surface, which is highly variable depending on topographical location, endogenous host factors and exogenous environmental factors. The cutaneous innate and adaptive immune responses can modulate the skin microbiota, but the microbiota also functions in educating the immune system.
As I’ve said before, our relationship with microbes should also be evaluated as an ecological issue. Completely germ-free environments are not necessarily the goal.