what happens when the immune system reacts to a food allergy? a. the allergens are broken down and deactivated by stomach acids. b. immunoglobulin e is produced and circulates in the blood. c. mast cells release antihistamines to counter the histamines. d. mast cells absorb and remove the offending food allergen from the bloodstream. e. the immune system develops tolerance after multiple exposures to the food allergen.