Food Sensitivity Testing

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Main Differences Between IgE and IgG Allergies

IgE Allergies vs. IgG Allergies: What is the difference?

What is the difference between an IgE and IgG allergy? Our team receives this question regularly. Here we will provide a brief overview of each type of allergic reaction.

IgE allergies (Type I allergies) are immediate responses to a foreign substance that has entered the body. These foreign substances can come from food or can come from inhalation. IgE allergies can cause very serious symptoms like difficulty breathing, swelling, and hives. In even more serious cases IgE reactions can lead to anaphylactic shock.

Releases histamine Does not release histamine
Tested by skin pricks No skin prick reaction
Anaphylactic shock No anaphylactic shock
Symptoms immediate Symptoms may be delayed
Most common allergy test Uncommon allergy test
Limited clinical usefulness Extreme clinical usefulness

Example of a typical IgE response:

Suppose a person with a peanut allergy eats a peanut. The B cells (white blood cells) in the body are exposed to the peanut allergens. The B cells begin making IgE antibodies to fight the peanut “infection”. These IgE antibodies were made specifically for defending the body against peanuts. The IgE antibodies bind to the peanut molecules or allergens in the body.

After the exposure to peanuts, IgE antibodies can also attach themselves to mast cells. There the IgE antibodies wait until the next peanut exposure. When the next peanut exposure occurs the IgE antibodies signal the mast cells to release histamine and other compounds. Histamine and these other compounds are the cause of allergy symptoms like itching and inflammation. All of this usually happens within minutes of ingesting the allergen. IgE allergies are treated with medications that block the release of histamines.

Next, we will discuss the role of IgG antibodies in an immune system reaction. The IgG antibodies are responsible for slower, more subtle reactions to foods that aren’t tolerated well.  The symptoms can range from headache and nausea, to fatigue or hyperactivity.  These symptoms may occur hours or even days after the offending food has been ingested making identifying the exact problem food nearly impossible. The degree and severity of symptoms vary with of the genetic makeup of the individual.  IgG testing identifies the reactive foods.  Elimination of IgG positive foods may bring about important improvements in symptoms of irritable bowel syndrome, autism, AD(H)D, cystic fibrosis, rheumatoid arthritis, and epilepsy as demonstrated in numerous clinical studies.


To learn more about IgG testing see our FAQ page.