Walking the fine line between cleanliness and sterility -- When is the time for aseptic technique?

Cara N. Wilder, Ph.D.

Photo provider: CDC/Kimberly Smith, Christine Ford

From the time we are very young, we are taught the aphorism "cleanliness is next to godliness".  Even now, we are bombarded by media advertising disinfecting wipes, anti-microbial soaps, and anti-bacterial hand-gels to sterilize every aspect of our daily life.  However, is this idea always the best policy for establishing a healthy lifestyle?  When is the time for aseptic technique versus general cleanliness?

Aseptic technique refers to the processes or procedures that are performed under sterile conditions.  Under these conditions, your equipment or local environment should be free of pathogenic microorganisms.  These techniques are routinely employed in both medical and laboratory environments where contamination with pathogenic microorganisms can result in hazardous conditions.  Aseptic techniques are also commonly used on a regular basis while dressing minor injuries or for the prevention of viral transmission during seasonal cold and flu epidemics.  But, how should we handle the daily messes, dirt, and grime that we come in contact with?  When does creating a sterile environment adversely affect your health?

Early childhood is when most individuals begin to interact with their environment and learn how to walk, speak, and develop proper eating and cleaning habits.  This critical stage in life is also when the immune system begins to develop and become the first line of defense against invading microorganisms.  It is at this developmental juncture where it is crucial that an individual is exposed to the vast array of naturally occurring microorganisms in the environment in order to not only establish a healthy microbial flora, but to enhance the maturation of the immune system.  

In medicine, the hygiene hypothesis states that the lack of early childhood exposure to environmental microorganisms increases the susceptibility to allergic disease via suppressing the natural development of the immune system.  In a recent study (Hanski et al., PNAS 2012), this concept was further advanced by the idea that "reduced contact of people with natural environmental features and biodiversity, including environmental microbiota, leads to inadequate stimulation of immunoregulatory circuits".  In this study, the allergic disposition (atopic sensitization) was analyzed in a random sample of adolescents living in a heterogeneous region.  They found that as compared to healthy individuals, atopic teens had lower environmental biodiversity in their surroundings in addition to significantly lower genetic diversity of gammaproteobacteria within their skin microflora.  These results correlated with the expression of IL-10, a key anti-inflammatory cytokine involved in immunological tolerance.  Generally, IL-10 expression was positively related with the abundance of gammaproteobacteria localized on the skin of healthy individuals.  Overall, these results suggest that environmental biodiversity, the human microbiome, and the human immune system are complex interwoven systems whose interactions are crucial for overall health and general well-being.  These results also suggest that the lack of environmental biodiversity is strongly associated with the development of allergies.

All in all, life can get a little messy -- what is important is how you deal with the mess.  Sometimes, a little dirt can go a long way.