Food sensitivity testing: should I be tested?

Food allergy (IgE-mediated)

A true food allergy means your immune system overreacts to a food. It can cause hives, swelling, wheezing, or throat tightness. These can start within minutes of eating. A severe reaction is called anaphylaxis and is an emergency. Doctors diagnose food allergy using your history plus a skin or blood test for that specific food. Testing many foods at once, without a reason, causes false results. The best confirming test is an eating challenge done in a clinic. This is different from a general food sensitivity panel, which is not a real allergy test. If your history points to one food, testing that food is worth doing.

Mast cell activation syndrome (MCAS)

Mast cell activation syndrome, or MCAS, is a rare condition. Mast cells are immune cells that release chemicals like histamine. In MCAS, they release too much, too often. This can cause flushing, hives, low blood pressure, or stomach pain. Symptoms happen again and again, affect more than one body system, and improve with mast cell medications. A blood test called tryptase, taken during a reaction, helps confirm it. MCAS has strict rules for diagnosis. It is often suspected but rarely confirmed, because many other conditions cause similar symptoms. A specialist should be involved before this diagnosis is accepted.

"Food sensitivity" (IgG/IgG4 panel result)

Not a recognized medical diagnosis — here’s what it usually means and what to ask about instead.

You may have had a blood test that reported sensitivity to many foods. These are usually IgG or IgG4 antibody panels. Having these antibodies is normal. They show past contact with a food, not a problem with it. Healthy people without any symptoms often test positive to the same foods. No major allergy society uses this test to diagnose food problems. Cutting out many foods based on this result can be unhelpful, and sometimes harmful. Your symptoms are real. If a true allergy is suspected, a different, validated test can check for that instead.

Histamine intolerance

Not a recognized medical diagnosis — here’s what it usually means and what to ask about instead.

Some people react badly to foods high in histamine, like aged cheese, wine, or leftovers. This is sometimes called histamine intolerance. The symptoms, like flushing, headache, or stomach upset, are real. The trouble is there is no reliable test for it. A blood test called DAO is sometimes offered, but low levels also occur in healthy people. Researchers agree there is no proven way to test for this condition yet. The best way to check is a careful trial of a lower-histamine diet, ideally with a dietitian. This is different from a true allergy, and it does not need allergy testing.