Food allergy is usually in the differential diagnosis when gastrointestinal symptoms are present but often overlooked in the diagnosis of other common conditions.

Even in the context of celiac disease, when the putative allergen has been eliminated via compliance with a gluten-free diet, additional food allergies have been reported to complicate the clinical picture, thus suggesting the need for food allergy testing among diagnosed celiac patients^{1, 2}. Yet peer reviewed reports indicate that IgE allergy testing (using RAST or ELISA methods) are unsatisfactory tools for identifying most food hypersensitivities. This is usually the case because food reactions are more often associated with delayed reactions^{3, 4}.

Further, 93% of patients with immediate reactions to foods also have delayed reactions to foods³. Delayed reactions would not be revealed through IgE testing. Hence, even patients with immediate type food allergies would benefit from testing for delayed immunological reactions to foods. IgG antibodies are correlated with gut inflammation and elevated numbers of alpha/beta intra epithelial lymphocytes⁴ which herald the presence of allergies to foods containing cereal grains.

Medical investigators and clinicians are increasingly turning to IgG antibody testing to identify specific dietary allergens that individual patients should be avoiding for better control over their symptoms^{5, 6, 7, 8}. Not only are IgG antibodies the most common of these immune proteins, they are highly sensitive to a variety of pathologies whether the target organ is the gut⁴, the cerebellum, or the peripheral nervous system⁵. Researchers report that IgG antibodies are likely to reflect a “local immune response of the gut” ⁴ thus giving rise to the growing preference for IgG food allergy testing. Some investigators report that in double blind studies IgG testing and strict dietary exclusion of the identified antigens has resulted in a 26% reduction in IBS symptoms⁶. These patients also showed significant reductions in non-colonic symptoms, including anxiety and depression, as well as improvements in measures of quality-of-life, among those who strictly complied with dietary exclusion of allergens as identified by IgG testing. Isolauri et al. call for further research into the dynamics of IgG mediated reactions based on the above findings⁷. They go on to suggest that IgG antibodies may play an important role in both IBS and food allergies because of the reported symptom reductions in IBS patients who comply with “elimination diets” based on IgG antibody testing.

A wide variety of ailments have recently been reported in association with food allergies. From sleep disturbances³ to a range of neurological ailments^{9, 10} to attention deficit hyperactivity disorder¹¹ to learning disabilities¹² to psoriasis vulgaris¹³ and other autoimmune skin conditions ¹⁵, to asthma ⁸, food allergies are significantly overlooked as a contributing factor. And yet, dietary exclusion of IgG identified allergens consistently results in amelioration of symptoms in a majority of antibody-positive patients^{5, 6, 7, 8, 13, 14}. Interestingly, high school students with multiple food allergies show significantly higher titers to intestinal microflora, suggesting increased intestinal permeability as a root cause at least in these cases of multiple food allergy¹⁵.

Available data suggest a pathogenic mechanism in at least some cases of food allergy. Examination of the peer-reviewed epidemiological literature suggests a rate of gluten sensitivity in ~12% of the general population 5 and 22% of adults surveyed report that one or more foods causes them to feel ill¹⁶, most commonly cow’s milk and wheat. On the basis of this epidemiological data alone, testing for IgG food sensitivities should be ordered for at least every fifth patient visiting a general practice. However, these data are based on general population studies. The true rate of such food sensitivities is likely much higher among groups who are visiting a physician. Most of these patients will have some physical complaint so testing for food sensitivities should occur more commonly than the general prevalence. Therefore, more than one quarter of most groups of patients seen in a general practice would likely benefit from food allergy testing.

Philip Putnam, M.D., of the Division of Pediatric Gastroenterology, Hepatology, and Nutrition, Food Allergy Clinic, at the Cincinatti Children’s Hospital Medical Center, decries the years of delayed diagnosis, patient suffering, and the familial frustration often associated with food allergies³. He also details five cases in which parents were wrongly accused of Munchausen’s by proxy. These concerned parents of food-allergic children continued to request testing and further medical investigation for their children³. They apparently refused to be dismissed on the basis of their children’s negative skin test results. The current trend of increasing recognition of immunological reactions to foods, at the cellular level, suggests the need for increased clinical suspicion of IgG mediated food allergies¹⁷. Given the evidence, it may be reasonable to suggest that perhaps even a majority of patients visiting a general practitioner should be investigated for food allergies.

References:
1. Bellanti JA, Sabra A, Zeligs BJ. Gastrointestinal immunopathology and food allergy. Ann Allergy Asthma Immunol. 2004 Nov;93(5 Suppl 3):S26-32.
2. Barbato M, Viola F, Russo LL, Lucarelli S, Frediani T, Cardi E. Microscopic and collagenous colitis in treated celiac disease due to food allergy? Gastroenterology. 1999 Mar;116(3):778.
3. Putnam PE. The mother of all food allergies. J Pediatr. 2003 Jul;143(1):7-9. (Food Allergy General)
4. Linkosalo L, Kaila M, Ashorn M, Turjanmaa K, Haapala AM, Karikoski R, Holm K. Alpha/beta intraepithelial lymphocytes, serum gliadin antibodies and allergy test positivity in children. Acta Paediatr. 2004 Jan;93(1):17-21.
5. Hadjivassiliou M, Grunewald RA, Davies-Jones GA. Gluten sensitivity: a many headed hydra. BMJ. 1999 Jun 26;318(7200):1710-1.
6. Atkinson W, Sheldon TA, Shaath N, Whorwell PJ. Food elimination based on IgG antibodies in irritable bowel syndrome: a randomised controlled trial. Gut. 2004 Oct;53(10):1459-64.
7. Isolauri E, Rautava S, Kalliomaki M. Food allergy in irritable bowel syndrome: new facts and old fallacies. Gut. 2004 Oct;53(10):1391 -3.
8. Yusoff NA, Hampton SM, Dickerson JW, Morgan JB. The effects of exclusion of dietary egg and milk in the management of asthmatic children: a pilot study. J R Soc Health. 2004 Mar;124(2):74-80.
9. Hadjivassiliou M, Grunewald RA, Davies-Jones GA. Gluten sensitivity as a neurological illness. J Neurol Neurosurg Psychiatry. 2002 May;72(5):560-3. (gluten sens neurological)
10. Bushara KO, Nance M, Gomez CM. Antigliadin antibodies in Huntington's disease. Neurology. 2004 Jan 13;62(1):132-3.
11. Schnoll R, Burshteyn D, Cea-Aravena J. Nutrition in the treatment of attention-deficit hyperactivity disorder: a neglected but important aspect. Appl Psychophysiol Biofeedback. 2003 Mar;28(1):63-75.
12. Knivsberg AM. Urine patterns, peptide levels and IgA/IgG antibodies to food proteins in children with dyslexia. Pediatr Rehabil. 1997 Jan-Mar;1(1):25-33.
13. Michaelsson G, Ahs S, Hammarstrom I, Lundin IP, Hagforsen E.Gluten-free diet in psoriasis patients with antibodies to gliadin results in decreased expression of tissue transglutaminase and fewer Ki67+ cells in the dermis. Acta Derm Venereol. 2003;83(6):425-9.
14. Perr HA. Novel foods to treat food allergy and gastrointestinal infection.Curr Gastroenterol Rep. 2004 Jun;6(3):254-60.
15. Fukuda S, Ishikawa H, Koga Y, Aiba Y, Nakashima K, Cheng L, Shirakawa T. Allergic symptoms and microflora in schoolchildren. J Adolesc Health. 2004 Aug;35(2):156-8.
16. Woods RK, Stoney RM, Raven J, Walters EH, Abramson M, Thien FC.Reported adverse food reactions overestimate true food allergy in the community. Eur J Clin Nutr. 2002 Jan;56(1):31-6.
17. Latcham F, Merino F, Lang A, Garvey J, Thomson MA, Walker-Smith JA, Davies SE, Phillips AD, Murch SH. A consistent pattern of minor immunodeficiency and subtle enteropathy in children with multiple food allergy. J Pediatr. 2003 Jul;143(1):39-47.

Reprinted with permission by: Ron Hoggan and Immuno Laboratories, Inc.
Publish date: 04/06/05

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