Most of us are familiar with the allergies that cause immediate anaphylactic symptoms such as difficulty breathing, hives, redness, itchiness, and swelling. In these reactions, the allergic foods cause the body to produce IgE antibodies and the response is known as a Type I immediate hypersensitivity.

A lesser recognized allergic reaction, called a Type III delayed hypersensitivity, instead produces IgG antibodies. IgG reactions take hours or days to develop, and since this type of reaction does not occur immediately, identifying the responsible foods can be difficult, especially when multiple foods are involved.

IgG allergy testing can help identify undiagnosed food allergies that may be contributing to symptoms or illness. The test needs only a simple finger prick to collect a small sample of blood, which is then sent to a laboratory where it is tested for IgG reactivity against 96 common foods.

These delayed allergic reactions can contribute to a variety of health problems including: headaches, high blood pressure, mood disorders, asthma, eczema, irritable bowel disease, joint pain, runny noses and puffiness around the eyes.

In a delayed hypersensitivity reaction, the IgG antibodies produced by the body attach themselves to the food allergen and create an antibody-allergen complex. These complexes are normally removed by special cells called macrophages, however, if they are present in large numbers, and the allergen is still being consumed, the macrophages are not able to keep up. As a result, the antibody-allergen complexes accumulate and are deposited in body tissues, leading to inflammation that can contribute to disease.

Weight Gain: Antibody-allergen complexes in tissue cause inflammation, which causes fluid retention and weight gain. To fight inflammation, the body releases a hormone called ghrelin, which also happens to be an appetite stimulant. Thus, IgG food reactions can cause weight gain in two ways: fluid retentionand increased appetite.

Digestive Disorders: Conditions like irritable bowel syndrome (IBS) have been linked to IgG food allergies. Studies have shown that elimination of foods producing an IgG reaction can alleviate IBS symptoms.

Mood and Attention Deficit Disorders: Deposition of antibody-allergen complexes in nervous system tissues may contribute to hyperactivity, depression, anxiety, inability to concentrate and other mood disorders. There is some evidence that eliminating IgG food allergens improves attentiveness in children.

Other Conditions: Antibody-allergen complexes can be deposited in any tissue and cause symptoms over time. For example, complexes deposited in lung tissue can cause asthma or other respiratory problems; in skin tissue, eczema may result; in blood vessels, hypertension or headaches may emerge; in joints, joint pain could occur; and so on, depending on the tissues involved.