Editing Anaphylaxis (section)

==Diagnosis==
Anaphylaxis is diagnosed on the basis of a person's signs and symptoms.<ref name=World11/> When any one of the following three occurs within minutes or hours of exposure to an allergen there is a high likelihood of anaphylaxis:<ref name=World11/>
# Involvement of the skin or mucosal tissue plus either [[Respiratory distress|respiratory difficulty]] or a low [[blood pressure]] causing symptoms
# Two or more of the following symptoms after a likely contact with an allergen:
#: a. Involvement of the skin or [[Mucous membrane|mucosa]]
#: b. [[Respiratory distress|Respiratory difficulties]]
#: c. [[Hypotension|Low blood pressure]]
#: d. [[Human gastrointestinal tract|Gastrointestinal]] symptoms
# Low blood pressure after exposure to a known allergen

Skin involvement may include: hives, itchiness or a swollen tongue among others. Respiratory difficulties may include: shortness of breath, [[stridor]], or low oxygen levels among others. Low blood pressure is defined as a greater than 30% decrease from a person's usual blood pressure. In adults a systolic blood pressure of less than 90 mmHg is often used.<ref name=World11/>

During an attack, blood tests for [[tryptase]] or [[histamine]] (released from mast cells) might be useful in diagnosing anaphylaxis due to insect stings or medications.<!-- <ref name=World11/> --> However these tests are of limited use if the cause is food or if the person has a normal [[blood pressure]],<ref name=World11/> and they are not [[Sensitivity and specificity|specific]] for the diagnosis.<ref name=His11/>

===Classification===
There are three main classifications of anaphylaxis.
# '''Anaphylactic shock''' is associated with systemic [[vasodilation]] that causes [[Hypotension|low blood pressure]] which is by definition 30% lower than the person's baseline or below standard values.<ref name=Shock10>{{cite journal|last=Limsuwan|first=T|author2=Demoly, P|title=Acute symptoms of drug hypersensitivity (urticaria, angioedema, anaphylaxis, anaphylactic shock)|journal=The Medical Clinics of North America|date=July 2010|volume=94|issue=4|pages=691–710, x|pmid=20609858|url=http://smschile.cl/documentos/cursos2010/MedicalClinicsNorthAmerica/Acute%20Symptoms%20of%20Drug%20Hypersensitivity%20(Urticaria,%20Angioedema,%20Anaphylaxis,%20Anaphylactic%20Shock).pdf|doi=10.1016/j.mcna.2010.03.007|url-status=dead|archive-url=https://web.archive.org/web/20120426041514/http://smschile.cl/documentos/cursos2010/MedicalClinicsNorthAmerica/Acute%20Symptoms%20of%20Drug%20Hypersensitivity%20%28Urticaria%2C%20Angioedema%2C%20Anaphylaxis%2C%20Anaphylactic%20Shock%29.pdf|archive-date=2012-04-26|access-date=2011-12-09}}</ref>
# '''Biphasic anaphylaxis''' is the recurrence of symptoms within 1–72 hours after resolution of an initial anaphylactic episode.<ref name="pmid32001253"/> Estimates of incidence vary, between less than 1% and up to 20% of cases.<ref name="pmid32001253"/><ref name=BI05/> The recurrence typically occurs within 8 hours.<ref name=CEA11/> It is managed in the same manner as anaphylaxis.<ref name=EAACI2014/>
# '''Anaphylactoid reaction''', '''non-immune anaphylaxis''', or '''pseudoanaphylaxis''', is a type of anaphylaxis that does not involve an allergic reaction but is due to direct mast cell degranulation.<ref name=CEA11/><ref name="His10">{{cite book |last=Ring |first=J |url=http://media.wiley.com/product_data/excerpt/42/04708611/0470861142.pdf |title=History and classification of anaphylaxis |author2=Behrendt, H |author3=de Weck, A |year=2010 |isbn=978-3-8055-9441-7 |series=Chemical Immunology and Allergy |volume=95 |pages=1–11 |doi=10.1159/000315934 |pmid=20519878}}</ref> Non-immune anaphylaxis is the current term, as of 2018, used by the [[World Allergy Organization]]<ref name=His10/> with some recommending that the old terminology, "anaphylactoid", no longer be used.<ref name=CEA11/>

===Allergy skin testing===
[[File:Allergy skin testing.JPG|thumb|upright=1.3|[[Skin allergy testing]] being carried out on the right arm]]
[[File:Epikutanni-test.jpg|thumb|upright=1.3|[[Patch test]]]]
[[Allergy test]]ing may help in determining the trigger. [[Skin allergy test]]ing is available for certain foods and venoms.<ref name=His11/> Blood testing for specific [[IgE]] can be useful to confirm milk, egg, peanut, tree nut and fish allergies.<ref name=His11/>

Skin testing is available to confirm [[penicillin]] allergies, but is not available for other medications.<ref name=His11/> Non-immune forms of anaphylaxis can only be determined by history or exposure to the allergen in question, and not by skin or blood testing.<ref name=His10/>

===Differential diagnosis===
It can sometimes be difficult to distinguish anaphylaxis from [[asthma]], [[Syncope (medicine)|syncope]], and [[panic attack]]s.<ref name=World11/> Asthma however typically does not entail itching or gastrointestinal symptoms, syncope presents with pallor rather than a rash, and a panic attack may have flushing but does not have hives.<ref name=World11/> Other conditions that may present similarly include: [[Scombroid food poisoning|scrombroidosis]] and [[Anisakis#Anisakiasis|anisakiasis]].<ref name=CEA11/>

===Post-mortem findings===
In a person who died from anaphylaxis, [[autopsy]] may show an "empty heart" attributed to reduced venous return from [[vasodilation]] and redistribution of intravascular volume from the central to the peripheral compartment.<ref name="v005">{{cite journal | last=Mustafa | first=S Shahzad | title=Anaphylaxis: Practice Essentials, Background, Pathophysiology | website=Medscape Reference | date=2024-02-26 | url=https://emedicine.medscape.com/article/135065-overview#showall | access-date=2024-06-18}}</ref> Other signs are laryngeal edema, eosinophilia in lungs, heart and tissues, and evidence of myocardial hypoperfusion.<ref name=DaBroi/> Laboratory findings could detect increased levels of serum [[tryptase]], increase in total and specific IgE serum levels.<ref name=DaBroi>{{cite journal|last=Da Broi|first=U|author2=Moreschi, C|title=Post-mortem diagnosis of anaphylaxis: A difficult task in forensic medicine|journal=Forensic Science International|date=Jan 30, 2011|volume=204|issue=1–3|pages=1–5|pmid=20684869|doi=10.1016/j.forsciint.2010.04.039}}</ref>