Are food allergies "immediate"?

No.  Reactions to foods can be immediate or delayed.  People are most familiar with immediate sensitivity food reactions.  Common offending foods include peanuts, strawberries, or fish.  Reactions will occur within seconds to hours after contact with the offending food.  Common reactions are hives or a skin rash, but some people may develop life-threatening anaphylactic reactions such as inability to breathe or internal swelling which may require immediate medical attention.  However, there is another kind of food sensitivity which occurs on a delayed basis.  Many patients and physicians are not as familiar with this kind of allergy, nor the testing, which is done through a blood test.  In this case, symptoms may not develop until several hours up until a few days after contact with the offending food.  Delayed food allergies may result in symptoms which are commonly regarded as arthritis, asthma, migraines, irritable bowel, or eczema.