IgE vs IgG vs IgA: Decoding Immunoglobulins

Immunoglobulins, better known as antibodies, come in several types, including IgE, IgG, and IgA, each triggering a different kind of immune response that ranges from immediate, life-threatening allergic reactions to slow-building chronic inflammation. Understanding these immunoglobulins and their differences is essential, especially when it comes to addressing food and inhalant immune responses and they are negatively impacting people’s health and overall wellness. In this blog, we'll decode the intricacies of IgE, IgG, and IgA.

Immunoglobulin E or IgE

Immunoglobulin E is associated with immediate hypersensitivity reactions with symptoms arising within minutes to hours of exposure. A way to remember the specifics of IgE is to think E is for emergency as IgE reactions can be sever or even life threatening. IgE reactions also known as allergies to foods and inhalants indicate that those food and inhalant triggers should be avoided completely.

IgE Symptoms:

The most known symptom of an IgE reaction is often anaphylaxis, specifically, swelling of the respiratory tract. IgE can have many other reactions including:

Testing for IgE food ALLERGIES:

Testing for food and inhalant allergies can be done using a food allergy test via skin prick where a small amount of an allergen is scraped onto the skin where the scraped area is observed for swelling and redness. This is very common and simple to do within office environments but is not the most accurate measurement, can be uncomfortable for patients, and limits the number of allergens that can be tested at a single time.

Blood testing is a more accurate measurement of allergies as it quantifies the specific IgE reaction to each analyte tested. Many blood tests utilize serum collections which allows many markers to be tested at a single time, at US BioTek we can test up to 98 markers, with little to no discomfort for the patient. As technology evolves, we are now able to run blood tests with finger stick micotainer collections and even dried blood spot cards making testing for IgE allergies something patients can do with little to no discomfort from their own home.

Immunoglobulin G or IgG

Immunoglobulin G or IgG, in this case IgG1-3, an antibody that can activate the pro-inflammatory complement system (complement cascade) associated with chronic inflammatory conditions. High levels of IgG (class II or higher) overload receptors and drive the inflammatory reaction while low levels of IgG (class 0/I) indicate tolerance.  

An IgG food sensitivity test is the most commonly performed food sensitivity testing and foods that are only high in IgG can often be safely re-introduced after a period of abstinence. 

IgG Symptoms:

Symptoms of an IgG mediated reactions are often delayed making it challenging to identify the correct culprit. Since symptom are often less sever and, in many cases, chronic, they are often blamed on things like aging. The most common IgG symptoms include:

Testing For IgG Sensitivities:

IgG testing is performed using food sensitivity tests, using blood samples to measure the immune response to the analytes tested. There are different testing methodologies that can be used to identify sensitivities, at US BioTek we pioneered the use of Enzyme-Linked Immunosorbent Assay (ELISA). It is now the gold standard in sensitivity testing as it has the largest body of peer reviewed research behind including independent studies that identify ELISA testing as being more accurate with higher rates of reproducibility when compared to other testing methods.

The ELISA method can use serum or dried blood spot cards making it simple to perform anywhere.

Immunoglobulin A or IgA

IgA are present in our mucus membranes and help us fight bacteria and virus pathogens. IgA is an antibody that can also activate the pro-inflammatory complement system associated with chronic inflammation. Unlike Secretory IgA (sIgA) in stool, which is two IgA molecules bounded together and secreted into the gut, serum IgA levels are associated with seasonal allergies and asthma. A Serum IgA reaction (IgA Sensitivities) to food triggers can indicate foods that are irritating the lining of the gut. 

IgA Symptoms:

Testing for IgA Sensitivities:

Testing for IgA sensitivities is the same process as IgG sensitivity testing; using a food sensitivities test. Often these tests will be run together in tandem providing specific insights into what food and inhalant triggers are causing patients symptoms, and how to create the most efficient treatment plans leading to increased clinical success.

Conclusion

In the intricate world of immunoglobulins, IgG, IgE, and IgA each have their roles in the body's immune responses. Understanding how they impact the body, the timing of reactions, and their relevance in food and inhalant immune responses is essential for healthcare providers. By leveraging this knowledge, practitioners can offer more precise and effective care, ultimately improving patient outcomes.

To learn more about food sensitivity testing and how to build panels specific to your patients needs visit https://www.usbiotek.com/food-sensitivity-testing

For more information on Allergy testing, visit https://www.usbiotek.com/allergy-testing

Frequently asked questions

What is the difference between IgE, IgG, and IgA antibodies?

IgE, IgG, and IgA are three types of immunoglobulins (antibodies) that drive different immune responses. IgE causes immediate allergic reactions, appearing within minutes to hours and ranging up to anaphylaxis ("E for emergency"). IgG is the most abundant antibody in the blood and is linked to slower, delayed responses, which is why food-specific IgG is used in functional medicine to investigate chronic, low-grade symptoms. IgA works mainly at mucosal surfaces — the gut, sinuses, and airways — where it helps defend the lining against pathogens.

Why are IgE allergic reactions immediate while IgG and IgA reactions are delayed?

IgE reactions are immediate because IgE antibodies are already attached to mast cells; on re-exposure to a trigger they release histamine within minutes, producing hives, swelling, or anaphylaxis. IgG- and IgA-associated reactions are thought to build more gradually, with symptoms like bloating, fatigue, brain fog, and headaches surfacing hours to days later — which makes the responsible food much harder to identify. Note that while delayed IgG/IgA food reactions are a foundation of functional-medicine practice, this model is debated within mainstream allergy and immunology.

Should I get IgE allergy testing or IgG/IgA food sensitivity testing?

IgE testing (skin prick or serum specific-IgE) is the validated tool for diagnosing true allergies, and a positive result usually means strict avoidance of that food. IgG and IgA food panels — often run by ELISA via serum or dried blood spot — are used in functional medicine to identify foods for a temporary elimination and reintroduction, not as a standalone diagnosis. Major allergy organizations note that IgG food testing is not validated to diagnose allergy or intolerance, so it's best used as one input within a clinician-guided elimination process.