What should you know about an IgG blood test for food allergy?

Food allergy is an immune reaction that can happen after exposure to a specific food and may involve rapid symptoms such as hives, swelling, vomiting, wheeze or an itchy throat. IgG detected against a food generally reflects exposure and is not the same measurement used to confirm an immediate allergic reaction. A result should therefore not be used alone to label a food unsafe or safe.

An allergist or clinician considers the timing, amount eaten, repeatability and symptoms. They may select validated allergy testing and, when appropriate, a medically supervised food challenge. Never test a suspected severe trigger by eating it at home.

Write down the food, amount, preparation, time to symptoms and every symptom that followed. Keep eating patterns stable until advice is available unless a clinician has told you to avoid a food. Do not make broad exclusions from an IgG panel, especially for children, without nutritional support. Ask about an allergy action plan if reactions have been rapid or involved breathing, circulation or widespread swelling.

Call emergency services immediately for trouble breathing, throat or tongue swelling, faintness, collapse, confusion, or symptoms affecting several body systems after eating. These can signal anaphylaxis and need emergency treatment. A mild isolated symptom still deserves clinical advice when it recurs, but an IgG report should never be used to judge the urgency of an active reaction.

Ask whether your episodes fit food allergy, which validated test is suitable, whether you need an emergency plan, and how to avoid accidental exposure without unnecessarily restricting your diet.