Helminth infections and allergic diseases are public health problems in different areas of the world. Helminths are usually prevalent and endemic in developing countries. However allergic diseases are more prevalent in developed countries and become increasing in urbanized areas of developing countries. Both diseases are characterized by Th2 type immune response: increased level of interleukin (IL)-4, IL-13, IL-5, Immunoglobulin E (IgE), eosinophilia and mastocytosis. Different epidemiological studies showed antithetical association between helminth infections and allergy in helminth endemic tropical regions. Acute and chronic helminth infections correlate with increased and decreased prevalence of allergy respectively. Different immunological mechanisms have been suggested for this difference. Increased level of polyclonal IgE and Modulated Th2 immune response (IgG4) are supposed to be produced during chronic helminth infections. Polyclonal IgE will bind on FcεR1 on the eosinophil, mast cell and basophil surface that inhibits the binding of allergen and parasite specific IgE on these cells and prevent subsequent degranulation. IgG4 also binds to epitopes on the allergen where allergen specific IgE will bind that again prevents cross-link of mast cell receptors. The state of helminth infections determines their impact on the development of allergy: Chronic and acute infections associate positively and negatively respectively with allergy. Keywords: Allergy, Helminth infections, IgE, Th2/Th1 type immunity

Keywords: Allergy, Helminth infections, IgE, Th2/Th1 type immunity