Helminths and the Hygiene Hypothesis

 

Full free text on when to introduce medicinal helminths.
“The ‘hygiene hypothesis’ takes a number of forms which are not exclusive, but have yet to be articulated as a unifying concept. An inverse relationship between parasite infection and immune disorders was first suggested by Greenwood, who noted the low incidence of rheumatoid arthritis in West Africa  [8], and then showed that mice and rats infected with rodent malaria were protected from autoimmune disease [9, 10]. Subsequently, the hygiene hypothesis became linked explicity to the setting of more developed countries when Strachan postulated that early-life exposure to common childhood infections protected younger siblings in larger families from developing allergies such as hay fever [11, 12]. At that time, soon after the emergence of the paradigm of opposing T helper type 1 (Th1) and Th2 arms of the immune system [13], this finding was interpreted as Th1-promoting viral and bacterial infections ‘educating’ the young immune system away from excessive and allergy-promoting Th2 responses. The core concept of infections imprinting the developing immune system has become embedded in most versions of the hygiene hypothesis, but the mechanistic explanation of opposing Th1/Th2 lineages has, over time, proved untenable.”