What are we doing to ourselves?

An interesting idea emerged from conversation over dinner with a colleague recently: While it is clear that hand hygiene is foundational for both hospital and community infection prevention, there may be an immunological price to the now all-pervasive focus on hand hygiene in the general population.

Let me explain. Hygiene is one of the pillars of public health and infection prevention, though we still struggle to practice what we know globally. Semmelweis showed us the need for clean hands in the clinical environment, and the notion of ridding hands of germs has evolved since then. Today, alcohol based hand rubs (ABHRs) are prominent in daily life. People rub their hands with "hand sanitizer" before eating out, after riding the bus, after using the restroom, and even at their desks throughout the day. What could possibly go wrong with such an awareness of hand hygiene?

Potentially, nothing. The importance of hand hygiene is undisputed and indisputable in infection prevention. That said, I often see people using ABHR very frequently throughout the day and it makes me wonder if such use of ABHR is eroding not only the transient flora of our hands, but also the resident flora. What is on our hands ultimately ends up challenging the immune system, via oral ingestion, absorption through rubbing the eyes, or inoculation via scrapes and cuts on the hands and fingers. Constantly challenging the immune system with a diversity of biologic agents gives rise to broad immunity.

Might we be eroding the frequency and diversity of that challenge, and thus the strength and diversity of the immunological protection, with such pervasive use of ABHR? This general notion, that cleanliness might have deleterious, unintended community-level consequences, is not new. It's been discussed within the context of polio, for example, and there is speculation about inverse relationships between cleanliness and asthma.

I'll close by noting that ABHR is but one of the several tools society currently employs to kill the spectrum of microbes in our immediate environment. There are also antimicrobial wipes and antimicrobial soaps. The weapons of mass microbial destruction are many and proliferating. They obviously have their place in the clinic but, regarding their sometimes near-obsessive use in the community, are they helping or hurting us in the long run?

(image source: David Hartley)

Semmelweis and hand hygiene

Dr Ignaz Semmelweis was a Hungarian born physician who worked in Vienna in the 1840s. He is popularly credited with the discovery of the importance of handwashing, though perhaps it's more accurate to say that he was among the first to appreciate the importance of hand hygiene, rather than handwashing.  Harbarth (2000) points out that

. . . many scientists have cited Semmelweis' observations, but, amazingly, grossly misleading impressions still arise about Semmelweis and his original idea of antiseptic hand disinfection, often wrongly cited as “handwashing” in the English-language literature. In fact, Semmelweis never promoted handwashing with soap and water; he was opposed to it, since he wrote: “The cadaveric particles clinging to the hands are not entirely removed by the ordinary method of washing the hands with soap.… For that reason, the hands of the examiner must be cleansed with chlorine, not only after handling cadavers, but likewise after examining patients”

Indeed, Semmelweis promoted a policy of using a solution of chlorinated lime (calcium hypochlorite) on the hands between autopsy work and the examination of patients, as opposed to soap.

So, let's celebrate Semmelweis' insights about the importance of the hands in infection prevention rather than associating his name with handwashing alone. He's recently come back on Twitter to help us -- and certainly we need that help. The WHO's World Hand Hygiene Day is May 5. Check out how you can help raise awareness about hand hygiene.

(image source: WHO)

Hand washing, rubbing, and posters

Every now and then one sees something that is obviously well intentioned and potentially even effective, but that is problematic nonetheless. A case in point is the poster shown at the right, proclaiming that "Alcohol-based handrubs kill bacteria more effectively than soap and water." Certainly they do, but that's not the point of handwashing with plain soap and water.

The purpose of handwashing with plain soap is to mechanically remove foreign material and microorganisms from the surface of the skin. It is not to kill microbes. Plain soaps have minimal, if any, antimicrobial activity. The purpose of alcohol-based handrubs (ABHRs) is to reduce the microbial burden on the skin to a safe level through the antimicrobial action of alcohol. Because handrubs do not remove organic material, they are not a substitute for washing visibly soiled hands. Moreover, ABHRs don't kill spore forming microorganisms such as Clostridium difficile or certain other pathogens of public health importance. Handwashing with soap and water is needed to remove such contamination. Antimicrobial soap combines the cleaning action of regular soap with antiseptic activity. 

These and related issues, such as when the different approaches are best used, are well covered by Manfred Rotter in chapter 91 of the 4th edition (2012) of the expansive text Hospital Epidemiology and Infection Control. Additional information can be found in the WHO guidelines on hand hygiene in healthcare and at a related CDC website. 

In the case of the poster above, it is available at a URL that is part of an interactive education module on hand hygiene for professional HCWs. The training itself, consistent with the poster, advises (on slide #19) that plain soaps are "good" at killing bacteria whereas ABHRs are "best" and antimicrobial soaps fall in between. I can't find evidence that plain soap kills bacteria or any other pathogen. Rather, plain soap removes pathogens by acting as a surfactant or detergent, and this seems to be well established in the literature. Perhaps "Remember to wash your hands -- Soap removes germs!" or "Alcohol-based hand rubs are often an effective alternative to soap for making your hands safe!" would have been more evidence-based, defensible, and constructive messages for a poster.

More importantly, if the overarching objective of hand hygiene -- preventing transmission of microorganisms via the hands -- is to be achieved, an awareness of the issues involved in the various approaches is needed. Knowing when to wash versus rub, and why, seems relevant to communicate widely.

(image source: CDC)