IgG (immunoglobulin G) food testing has increased in popularity over the past few years as patients and practitioners search for new answers to old health problems. The theory is that hidden food allergies may be at the root cause of many complicated health issues, and that elimination of these foods can result in a reversal of underlying pathology and symptoms.
Dermatological conditions in particular are multi-factorial and may not respond to conventional medical treatment, so both patients and doctors are turning to alternative solutions, including IgG testing. The tests have become so popular that a company called EverlyWell was recently funded on the TV show Shark Tank for $1,000,000. The company manufactures and sells direct-to-consumers an IgG blood test that can be done at home with the prick of a finger. But despite increased use of IgG testing, many questions remain regarding the validity of these tests, and some critics denounce them as worthless or even harmful.,
Food Allergy vs Food Sensitivity and Food Intolerance
Food allergies affect an estimated 5.9 million children and 9 million adults in the U.S. The CDC defines a food allergy as “a potentially serious immune response to eating specific foods or food additives”. Food allergies are representative of immediate IgE-mediated reactions and symptoms can range from mild (such as hives or an itchy mouth), to severe (such as anaphylaxis or death). These are considered Type I hypersensitivity reactions.
But there are some who believe that other types of food allergies involving IgG-mediated reactions could be to blame for chronic food-mediated disease such as gastrointestinal, autoimmune and dermatological problems. IgG-mediated responses are Type II hypersensitivity reactions (cytotoxic reactions against cell surface and extracellular matrix proteins) or Type III hypersensitivity reactions (antibodies that react with soluble antigens forming complexes that activate complement).
There is much confusion over terminology as the phrases “food allergy”, “food sensitivity” and “food intolerance” are not well-defined. Many people use them interchangeably, so it can be difficult to know what specific types of allergies and tests are being referred to, even in published literature. The Mayo Clinic defines a food allergy as “an immune system reaction that affects numerous organs in the body” and by default considers all other reactions to food as “food intolerance”, including: a lack of necessary enzymes (such as lactase), sensitivity to food additives, and Celiac disease. While ambiguity in the use of these terms exists, generally “food allergies” are considered IgE-mediated responses while “food sensitivities” and “food intolerances” are interchangeable terms meant to encapsulate physiologic responses that occur in the digestive system., Those who utilize IgG food sensitivity testing believe it can reveal and quantify non-IgE-mediated food reactions by identifying specific foods that trigger increased levels of IgG antibodies in a person.
IgE vs. IgG Testing
IgE food allergy testing
IgE-mediated food allergies can be tested for using serum IgE, skin prick, intradermal or patch testing with the most common tests being the first two. IgE serum tests generally use ELISA (Enzyme-Linked Immunosorbent Assay) to determine the level of IgE antibodies that are generated against a specific food or allergen (like peanuts or mold). All commercial antigens are prepared from raw food and IgE antibodies are measured against raw food antigens. In a skin prick test, a miniscule amount of an allergen is directly inoculated into a patient’s skin. If a wheal or erythema develops, the test is considered positive for that item.
IgG food sensitivity testing
IgG antibodies are also measured using ELISA tests and also utilize raw food antigens, same as IgE tests. The most common IgG tests include a panel of around 96 common foods organized by groups such as: dairy, meat/fowl, fruit, fish/crustacea/mollusk, grains/legumes/nuts, vegetables, and miscellaneous (coffee, sugar, etc.). Food antigens are placed into 96 separate wells and serum from an individual’s blood draw is introduced into each well. But exactly what is being measured and the methods used are not often transparent.
Different labs measure different combinations of total IgG, IgG1, and IgG4, and source antigens from different companies. It’s not clear if the antigens are taken from just a part of a food (such as the wheat germ vs the endosperm ), or if there has been cross-contamination with bacteria or fungi, all of which could affect the results.
Most IgG testing companies send a final report to the patient or doctor listing out the level of IgG antibodies for each food with various scales. The person or provider can then decide which foods to eliminate based on the results, with the end goal being an elimination of symptoms believed to be caused by food sensitivity. Costs for these tests are not covered by insurance and range from $100-$400.
Are High IgG Antibodies Indicative of a Problem?
Antigens on foreign substances stimulate the production of antibodies via circulating immunoglobins, thereby triggering an immune response in the body. IgG antibodies make up 70-75% of all immunoglobulins in circulation and are a main player in acquired immunity. There is a debate surrounding whether or not the production of IgG antibodies against foods is normal or whether it indicates a hypersensitivity reaction to specific foods. Some researchers argue that the production and binding of IgG antibodies to food antigens is a normal part of digestion, and actually signifies a well-functioning immune system in an individual and tolerance.,, Others argue that up to 15% of consumed protein is incompletely digested, and that these larger molecules are recognized as pathogens, thereby creating an inflammatory response which can lead to symptoms such as IBS, migraines and skin problems.
A study in 2004 tested 150 people with irritable bowel syndrome (IBS) for IgG food sensitivity. Participants were then randomized into two groups: one group was placed on a “true diet” and was instructed to remove all foods with raised IgG antibodies, while the other group was placed on a “sham diet” and told to exclude foods to which they did not have elevated antibodies. The IgG exclusion “true diet” group had a 10% reduction in symptom score compared to the sham diet group, and researchers concluded that further research based on eliminating high IgG antibody foods was merited.
Dermatological Conditions and Food Sensitivity
Many patients suffering from dermatological conditions such as acne, eczema and psoriasis have suspected food sensitivities have an impact on their condition. The vast majority of studies on food and dermatological conditions focus on IgE-mediated food allergies, but there are a few studies on the correlation between IgG antibodies and food elimination.
A study with 1,206 psoriasis patients asked them to self-report which foods they felt were triggers for their psoriasis. 63% of respondents reported food triggers, including in order of prevalence: sugar, alcohol, tomato, gluten, and dairy. No IgG serum testing was involved in this study, but researchers theorized that these foods may be causing dysbiosis and inflammation in the gut leading to an upregulation of the immune system. In another study on diet and psoriasis, patients with elevated IgG or IgA antibodies to gluten showed improvement on a gluten-free diet.
A study in Taiwan with 216 children attempted to determine the correlation between serum IgG and childhood eczema and allergy using ELISA testing. The results determined that IgG rates were higher in the eczema and allergy groups vs the control group, with milk and eggs causing the highest IgG response. Researchers concluded that examination of IgG antibodies in serum was useful in diagnosing and treating childhood eczema.
Validity of IgG Food Sensitivity Tests
Governing health bodies such as the Food and Drug Administration (FDA), the American Academy of Allergy, Asthma & Immunology (AAAA), the Canadian Society of Allergy and Clinical Immunology (CSACI), and the European Academy of Allergy and Clinical Immunology (EAACI) ,, have not yet accepted the validity of these tests. There is also a lack of published research showing the reproducibility and validity of these tests. A researcher from Bastyr University conducted a trial through the Bastyr Center for Natural Health. Six blood samples were taken from the same patient but labeled with different names and sent to three different laboratories performing IgG testing. There was a high variability of results both within an individual lab as well as between labs, and the researcher concluded that the validity of IgG food sensitivity was questionable. In another trial, a blood sample from a 33-year-old female patient was sent to four different IgG testing companies. The authors note “very little consistency was found among the results of the four tests measuring IgG- 79-83 percent disagreement.” Sixty-five foods were measure by all four labs, and of these, no food was shown as reactive by all four, whereas twelve foods were shown as non-reactive by all four. However, the report goes on to say that two of the IgG tests showed 100% specificity and PPV (positive predictive value) when compared to the results of the food elimination challenge.
As stated previously, both IgG and IgE food testing uses raw food antigens as substrates, but of course, humans prepare and consume much of their food processed in some form. A study conducted in 2009 questioned what would happen if IgE, IgG, IgA, and IgM testing was performed against processed food antigens. Results across the board showed that all antibody reactions against modified food antigens were higher than against raw food antigens. Researchers concluded that all immunoglobulin antibody testing would be improved if both raw and food antigens were used.
Elimination diets are the gold standard for determining food sensitivity in naturopathic medicine and have been used by naturopathic doctors (NDs) to treat a variety of complicated skin conditions including acne, eczema and psoriasis. An elimination diet involves having a patient remove foods that commonly cause allergies, but may not show up on food allergy tests. Common culprits include egg, wheat/gluten, dairy, corn, soy and sugar. Different versions of the diet eliminate foods for varying amounts of time ranging from two weeks to up to six months. After the elimination phase, a reintroduction phase is entered where a food is eaten three times a day for one day to see if symptoms return. If symptoms have not returned after 2-3 days, then the patient moves on to reintroducing the next food, and so it continues until all offending foods have been identified.
Elimination diets are difficult and depend on the individual to follow the protocol exactly, as any cheating invalidates the trial. Many patients are forced to cut out the very foods they eat on a daily basis and find it very difficult to give up these foods as well as to find acceptable alternatives. Results of elimination diets are highly varied and can range from a total eradication of a particular health issue to no change at all. It should be noted that elimination diets are meant to discover food sensitives only, and should not be performed to determine IgE-mediated food allergies as anaphylaxis and death could result.
Pros and Cons of IgG Testing
So, with a lack of industry support and published data, why do IgG food sensitivity tests continue to gain in popularity? While clinical experience has shown that food elimination may make a difference in dermatological conditions, the exact mechanism is unknown. And this is perhaps where the theory of IgG food sensitivity has gained proponents and why the market is growing. Both patients and practitioners want answers to health problems, and IgG tests purport to offer a new solution. In addition, there are patients and practitioners who claim to have benefited from IgG testing.
- Some positive research exists
- A few research reports support IgG testing for dermatological conditions such as eczema and psoriasis
- Data-driven patients can be motivated to do the elimination diet
- Because this diet is difficult, some patients need to see “evidence” that it’s necessary to cut out some of their favorite foods for a period of time
- It can make the elimination diet easier
- Reports may help direct patients as to which foods to remove first
- It is easy to perform
- One blood draw is all that is required
- Validity questions remain
- It is unclear if results are reproducible between labs or even within an individual lab
- It is unclear if increased IgG antibodies for specific foods means there is a problem, or if it’s just a part of normal digestive function
- It can stop patients from pursuing other appropriate treatments
- Patients may focus on food elimination at the expense of other therapeutic treatments which have been proven to help improve their condition
- IgG antibodies are not the only problems people may have with food sensitivity
- A negative test does not mean people don’t have other food sensitivities such as lactose intolerance or Celiac disease
- It is not suitable for people with eating disorders
- The intense focus on problems with and elimination of specific foods could exacerbate or creating eating disorders
- It is not covered by insurance
- Patients must pay out of pocket for these tests as none are covered by insurance
- Rule out underlying pathologies before attributing dermatological symptoms to food sensitivity issues
- Explain to patients the pros and cons of using IgG food sensitivity testing
- Call the lab you are interested in using to find out their methodologies and reproducibility rates or conduct your own trials with labs
- Consider doing an elimination diet with your patient even if IgG testing is negative. The elimination diet is still the gold standard for identifying food sensitivities and may identify non-IgG problems
- Explore other dermatological treatment plans beyond just an elimination diet
The decision of whether or not to use IgG food sensitivity testing ultimately belongs to patients and health practitioners. Doctors can help guide patients through the pros and cons of IgG sensitivity testing and ultimately through an elimination diet, if it seems appropriate. Perhaps in the future more research will reveal the underlying mechanism of how IgG antibodies react against food and whether IgG testing is a reliable way to address various health complaints. For now, the lack of widespread evidence and extensive validity concerns indicate that this should not be the only tool employed in the pursuit of improving symptoms and healing dermatological problems.