Brown Norway rats were primed intraperitoneally with beta-lactoglobulin for 3 wk to induce reaginic antibody, during which time they were fed diets containing 10% each of coconut oil (CO), high oleic safflower oil, safflower oil (SO), or fish oil, then they were challenged for 3 h orally with the antigen. The dietary SO, compared to other dietary fats, resulted in lower circulatory release of rat chymaseII (RChyII), an indicator of degranulation of mucosal mast cells in the intestine, in response to the antigen. Addition of 0.5% curcumin to the CO or SO diet lowered the release. The SO diet, compared to CO diet, tended to increase the concentration of reaginic antibody, but the influence of curcumin addition was not prominent. These results indicate that dietary ingredients differently influence the synthesis of immunoglobulin E and degranulation of mast cells.