Parasites and allergy: observations from Brazil.

Brazil is a middle-income country undergoing the epidemiological transition. Effects of changes in daily life habits and access to clean water, sanitation and urban services on a growing urban population have contributed to a double burden of both infectious and noncommunicable chronic diseases. Studies have indicated that parasite infections may modulate the human immune system and influence the development of allergic conditions such as asthma. However, there is no consensus in the published literature on the effects of parasitic infections on allergy, perhaps as a consequence of factors determining the epidemiology of these infections that vary between populations such as age of first infection, duration and chronicity of infections, parasite burden and species, and host genetic susceptibility. In this review, we discuss the observations from Brazil concerning the relationship between parasite infections and allergy.