The mast cell is the most important cell type participating in type -1 hypersensitivity reactions; mast cells also play a subsidiary role in the generation of hypersensitivity , and associated tissue damage, in some other immune phenomena.(Rimmer et al; 1984).The mast cell is widely distributed granulated, cellular component of most tissues, although it is more prevalent in the area that come into the frequent contact with the external environment such as skin, lungs, upper airways, and gastrointestinal tract(Barrett K.E et al; 1954). For larger worms as for gastrointestinal nematode the host will often develop inflammation and hypersensitivity. Gastrointestinal nematodes (A.galli) produce allergens in sensitized and hyper sensitized chicks. Proliferation of the mast cell is correlated with the dose of the egg antigen in sensitized and hyper sensitized chicks. The mast cell release pharmacological mediators that produce the inflammatory responses typical of type 1 hypersensitivity reactions. The` intestinal mast cell provide protective immunity against gastrointestinal nematodes. Experimental investigation show mastocytosis condition is more prevalent during parasitic infection.