This is a blood test that identifies delayed allergies (sometimes called sensitivities). Unlike "regular" allergies, delayed allergies can take up to 3 days to produce symptoms. Therefore they can often be difficult to identify without testing. If you have had skin testing for allergies, you were not tested for delayed allergies. Delayed allergies can be identified by a blood test called an ELISA test. This type of allergy testing is essential for identifying "hidden" allergies that may go undetected by traditional allergy testing methods.