Crab (f23) IgG4 details

This test measures IgG4 antibodies to crab proteins. IgG4 is a subclass of IgG antibodies that the body tends to make after repeated exposure to a food, so people who eat crab regularly often have measurable levels. A higher result generally shows exposure, and IgG4 is often seen as a sign of tolerance rather than allergy. It does not measure the IgE antibodies involved in classic shellfish allergy; that requires an IgE test. Food IgG reflects exposure to a food your immune system has encountered, and its link to symptoms is debated, so a result should not be used on its own to diagnose food allergy or intolerance or to remove foods from your diet.