Parasitic infections have been one of the major health problems in Thailand for decades.However, the prevalence of parasitic infections has decreased considerably in recent years due to an increase in personal hygiene and public sanitation. In contrast, allergic diseases, their morbidity, and mortality appear to be on the rise. An immunological explanation and epidemiologic relationship between parasitic infections and allergies has been espoused since the late 1980s. The hygiene hypothesis has been the internationally recognized theory to explain the findings. IgE blocking hypothesis and the modified Th2 responses have also been purposed to describe the effect of preventing allergic diseases by parasitic infections and by IgG4 inducing tolerance, respectively. Several lines of evidence have suggested an inverse association between parasitic infections and the presence of allergic symptoms. Moreover, data have demonstrated interleukin-10 presenting the suppressive effect of parasitic infection to allergic responses. Nevertheless, a causal relationship between parasitic infections and allergies remains to be proven. Future prospective and intervention studies are required to determine the role of parasitic infection with allergic responses to host exposures.

Keywords: Parasite, Parasitic infection, Allergy, Hygiene hypothesis, IgE, Cross-reactivity, IL-10