Editing Food intolerance (section)

==Diagnosis==
Diagnosis of food intolerance can include [[hydrogen breath test]]ing for lactose intolerance and [[fructose malabsorption]], professionally supervised [[elimination diet]]s, and [[ELISA]] testing for IgG-mediated immune responses to specific foods. It is important to be able to distinguish between food allergy, food intolerance, and autoimmune disease in the management of these disorders.<ref name="pmid9196849">
{{cite journal |author=Kitts D |title=Adverse reactions to food constituents: allergy, intolerance, and autoimmunity |journal=[[Can J Physiol Pharmacol]] |volume=75 |issue=4 |pages=241–54 |year=1997 |pmid=9196849 |doi=10.1139/cjpp-75-4-241 |name-list-style=vanc|author2=Yuan Y |author3=Joneja J |display-authors=3 |last4=Scott |first4=F. |last5=Szilagyi |first5=A. |last6=Amiot |first6=J. |last7=Zarkadas |first7=M.}}</ref> Non-IgE-mediated intolerance is more chronic, less acute, less obvious in its clinical presentation, and often more difficult to diagnose than allergy, as skin tests and standard immunological studies are not helpful.<ref name="pmid10565387" /> Elimination diets must remove all poorly tolerated foods, or all foods containing offending compounds. Clinical investigation is generally undertaken only for more serious cases, as for minor complaints which do not significantly limit the person's lifestyle the cure may be more inconvenient than the problem.<ref name = "Clarke" />

Immunoglobulin (IgG) tests measure the types of food-specific antibodies present. There are four types of IgG, IgG1 makes up 60-70% of the total IgG, followed by IgG2 (20-30%), IgG3 (5-8%), and IgG4 (1-4%). Most commercially available tests only test for IgG4 antibodies, however some companies such as YorkTest Laboratories test for all four types.<ref>{{Cite web|title=What is the difference between IgG food intolerance tests?|url=https://www.yorktest.com/what-is-igg/|access-date=2020-07-09|website=YorkTest|language=en-GB}}</ref>

IgG4 only tests are debatably invalid; IgG4 presence indicates that the person has been repeatedly exposed to food proteins recognized as foreign by the immune system which is a normal physiological response of the immune system after exposure to food components.<ref name="pmid18489614">
{{cite journal |author=Stapel SO |title=Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report |journal=Allergy |volume=63 |issue=7 |pages=793–6 |date=July 2008 |pmid=18489614 |doi=10.1111/j.1398-9995.2008.01705.x |url=http://www.zora.uzh.ch/id/eprint/14049/1/IgG4.pdf |name-list-style=vanc|author2=Asero R |author3=Ballmer-Weber BK |display-authors=3 |last4=Knol |first4=E. F. |last5=Strobel |first5=S. |last6=Vieths |first6=S. |last7=Kleine-Tebbe |first7=J. |last8=Eaaci Task |first8=Force|s2cid=14061223 }}</ref><ref name=":0" /> Although elimination of foods based on IgG-4 testing in [[Irritable bowel syndrome|IBS]] patients resulted in an improvement in symptoms,<ref>{{cite journal|pmid=15361495|year=2004|last1=Atkinson|first1=W|last2=Sheldon|first2=TA|last3=Shaath|first3=N|last4=Whorwell|first4=PJ|title=Food elimination based on IgG antibodies in irritable bowel syndrome: A randomised controlled trial|volume=53|issue=10|pages=1459–64|doi=10.1136/gut.2003.037697|pmc=1774223|journal=Gut}}</ref> the positive effects of food elimination were more likely due to wheat and milk elimination than IgG-4 test-determined factors.<ref>{{cite journal|pmid=    16009694|year=2005|last1=Hunter|first1=JO|title=Food elimination in IBS: the case for IgG testing remains doubtful|volume=54|issue=8|pages=1203|pmc=1774875|journal=Gut}}</ref> The IgG-4 test specificity is questionable as healthy individuals with no symptoms of food intolerance also test positive for IgG-4 to several foods.<ref>{{cite journal|pmid=7487363|year=1994|last1=Kruszewski|first1=J|title=High serum levels of allergen specific IgG-4 (asIgG-4) for common food allergens in healthy blood donors.|volume=42|issue=4|pages=259–61|journal=Arch Immunol Ther Exp (Warsz)}}</ref>

Diagnosis is made using medical history and cutaneous and serological tests to exclude other causes, but to obtain final confirmation a double blind controlled food challenge must be performed.<ref name="pmid16782524" /> Treatment can involve long-term avoidance,<ref>{{cite web |url= http://www.healthyfutures.com/allergiesandsymptoms/allergy-sensitivity-intolerance |title= What's the difference between an allergy, an intolerance and a sensitivity? |author= Editorial Staff |publisher= Healthy Futures |access-date= 24 August 2010 |archive-url= https://web.archive.org/web/20101116171457/http://www.healthyfutures.com/allergiesandsymptoms/allergy-sensitivity-intolerance |archive-date= 16 November 2010 |url-status= dead}}</ref> or if possible re-establishing a level of tolerance.

The [[antigen leukocyte cellular antibody test]] (ALCAT) has been commercially promoted as an alternative, but has not been reliably shown to be of clinical value.<ref name="pmid16047707">{{cite journal |author=Wüthrich B |title=Unproven techniques in allergy diagnosis |journal=J Investig Allergol Clin Immunol |volume=15 |issue=2 |pages=86–90 |year=2005 |pmid=16047707 |url=http://www.jiaci.org/issues/vol15issue02/1.pdf }}</ref><ref name="pmid20200768">{{cite journal |journal=Singapore Med J  |date=January 2010 |volume=51 |issue=1 |pages=4–9 |title=Diagnostic tests for food allergy |vauthors=Gerez IF, Shek LP, Chng HH, Lee BW |pmid=20200768 }}</ref><ref name="pmid16097911">
{{cite journal |journal=Med J Aust |year=2005 |volume=183 |issue=4 |pages=173–4 |author1=Mullins Raymond J |author2=Heddle Robert J |author3=Smith Pete |title=Non-conventional approaches to allergy testing: reconciling patient autonomy with medical practitioners' concerns |url=http://www.mja.com.au/public/issues/183_04_150805/mul10358_fm.html|pmid=16097911|doi=10.5694/j.1326-5377.2005.tb06986.x |s2cid=30242205 |url-access=subscription }}</ref>