By Helenka Rowe
As science and technology have advanced, so have our methods of disinfecting the world around us. In a developed country like the United States, we have antibacterial soaps, scrubs, and wipes at our disposal through every part of the day - from home, to workplace, to public places. Our children are protected from too much exposure to anything “dirty.” We even have the “5 Second Rule” for how long food is still edible after it has fallen on the ground.
Recently, however, strong evidence has been published supporting the hygiene hypothesis, which was originally presented by D.P. Strachan in 1989. Strachan observed that the allergic diseases of hay fever and eczema were less common in children from larger immediate families. Did children who were exposed to more infectious agents by their numerous siblings have more protection from allergies later in life?
With a greater appreciation for the intricacies of the immune system, this theory has been revisited in epidemiologic and immunologic circles. Allergies are an abnormal reaction of the immune system to harmless environmental substances and have been rising in prevalence over the past few decades, especially in developed countries (Grammatikos, 2008). One of the current explanations for the increase in allergic (or atopic) diseases is that the immune system needs exposure to a certain variety of foreign antigens to mature correctly (Grammatikos).
Helminths and Other Parasites
Worms have been found to be therapeutic in treating certain diseases. In countries like the U.S., parasites are an uncommon health problem, and seem to be the opposite of a medical intervention. However, infection with such a parasite, known as a helminth, shifts the immune response to one specific to worms, and thus reduces the immune response that may be causing diseases such as ulcerative colitis, Crohn’s, reactive airway disease, encephalitis and diabetes (Elliot, et al, 2006). In fact, treatments that take advantage of this natural immunologic shift have been successfully used in a variety of patients (Osada, 2010).
According to CU immunologist J.J. Cohen, the incidence of autoimmune and hypersensitive diseases continues to rise in the developed world, while the incidence of these diseases in the developing world (where parasite infection is quite common) is very low. Though many parents naturally think that protecting their children means sterilizing their toys and avoiding contact with public property, the truth may actually lie in a balance between hygiene and helminths. As Cohen suggests, “the new rule should be that if it falls on the floor and still looks like food 30 seconds after you pick it up, then it’s edible.”
Helenka Rowe is a second year medical student at the University of Colorado. She graduated from Colorado State University with a degree in biology, is currently interested in pediatrics, and hopes to practice medicine in an underserved community.
Elliott DE, Summers RW, Weinstock JV. “Helminths as governors of immune-mediated inflammation.” Int J Parasitol. 2007 Apr;37(5):457-64. Epub 2006 Dec 28.
Grammatikos AP. “The genetic and environmental basis of atopic disease.” Ann Med, 2008. 40(7): 482- 95
McKay, DM. “The therapeutic helminth?” Trends Parasitol. 2009 Mar;25(3):109-14. Epub 2009 Jan 23.
Osada, Y, Kanazawa T. “Parasitic Helminths: New Weapons against Immunological Disorders” J Biomed Biotechnol. 2010; 2010: 743758. Published online 2010 February 10. doi: 10.1155/2010/743758.
Strachan, D.P. “Hay fever, hygiene, and household size.” BMJ. 1989 November 18; 299(6710): 1259– 1260.