Is it possible to be too clean?
The “hygiene hypothesis”, first proposed in 1989, suggests that excessive cleanliness could be responsible for the observed increase in allergies and autoimmune diseases in developed countries over the last century. These disorders remain rare in developing nations, where life-threatening infectious diseases remain common.
Allergies occur when your immune system overreacts to allergens in the environment, or in certain foods (e.g. peanuts) and toxins (e.g. bee stings). Drugs can also trigger an allergic reaction. Symptoms range from mild swelling, watery eyes and sneezing to life-threatening anaphylaxis.
Proponents of the hygiene hypothesis believe that exposure to a variety of microorganisms early in life teaches the immune system how to react to foreign substances. The theory goes that when young children grow up in “sterile” environments their exposure to harmless and beneficial microorganisms as well as to pathogens is reduced.
Supposing this hypothesis to be true, it still needs to be put in perspective.
As infectious disease expert Dr Michael Bell puts it, “Living more sanitarily may have increased asthma, but in terms of scale and impact, that’s tiny compared with the benefit of not dying from disease for lack of hygiene”. (Source 1)
Indeed, deaths from infectious diseases have declined by over 96% in the past century in Australia. (Source 2)
Emphasis should be placed on moderation and common sense. Practise and teach good personal hygiene, clean your home well, particularly areas like the bathroom and the kitchen, but don’t cloister children from all dirt. Use antibacterial cleaners in areas and situations where they are most needed, and of course the strictest infection control practices must still be followed in health care settings and food production facilities.
Source 1: “Can dirt do a little good?”, Wall Street Journal, May 17 2010
Source 2: AIHW 2005 “Mortality over the twentieth century in Australia: Trends and patterns in major causes of death." Mortality Surveillance Series no. 4