What happens with an allergic reaction to food?

Often delayed rxn: Foods must generally first be digested, then absorbed into the body so reactions to them are usually delayed and are igg reactions. One often thinks of the peanut allergy that is immediate and deadly which is and ige reaction. The reactions can vary from diarrhea to constipation, skin rashes, joint pains, hair loss and more so testing with a specialty igg blood test is required to "figure it out".