In Canada, angioedema is managed by allergy & immunologists. Angioedema is sudden, asymmetric, non-pitting swelling of the deeper dermis, subcutaneous tissue, or submucosa, most often involving the lips, eyelids, tongue, larynx, hands, feet, or genitals. Around 15-25% of people develop at least one episode in their lifetime, and roughly half of acute episodes seen in emergency departments are allergic (histaminergic) in origin, triggered by foods, drugs, latex, or insect stings.
Angioedema (ICD-10: T78.3 for allergic; D84.1 for hereditary C1 inhibitor deficiency) is localized, transient, well-demarcated swelling of the deep dermis and subcutaneous or submucosal tissue caused by plasma leakage from postcapillary venules. Two distinct molecular pathways drive the syndrome. Histamine-mediated (mast cell) angioedema, the focus of this page, accompanies most acute allergic reactions and chronic urticaria, develops within minutes to two hours, responds to antihistamines, corticosteroids, and adrenaline, and is frequently itchy and accompanied by hives. Bradykinin-mediated angioedema includes hereditary angioedema (HAE) from C1 esterase inhibitor deficiency, acquired C1-INH deficiency, and ACE-inhibitor-induced angioedema; these forms develop over hours, last longer, do not itch, do not respond to adrenaline or antihistamines, and need bradykinin pathway blockers or plasma-derived C1-INH.
The key symptoms of Angioedema are: Rapid, non-pitting, asymmetric swelling of the lips, eyelids, tongue, cheeks, or genitals that develops over minutes to two hours and resolves over 24-72 hours., Itching, burning, or tingling at the swelling site (typical of histaminergic forms; bradykinin-mediated angioedema is non-itchy)., Urticarial wheals (hives) on the trunk, arms, or legs accompanying the deeper swelling in roughly 50% of allergic episodes., Throat tightness, hoarseness, drooling, or stridor from laryngeal involvement — a life-threatening sign requiring immediate adrenaline., Abdominal pain, cramps, nausea, vomiting, or diarrhea from bowel-wall edema, more common in bradykinin-mediated forms but seen in severe allergic episodes too., Tongue swelling that distorts speech and may obstruct the airway within 10-30 minutes., Eye swelling (periorbital edema) closing one or both eyes shut, usually unilateral or asymmetric..
Diagnosis is clinical. The history establishes timing (minutes to hours), associated urticaria or itching (supports histaminergic), accompanying anaphylactic features (hypotension, bronchospasm), recent drug or food exposures, and family history (raises suspicion for hereditary angioedema). Physical examination during an attack confirms non-pitting, asymmetric, well-demarcated swelling without erythema in bradykinin forms or with surrounding flush and wheals in histaminergic forms. Laboratory tests confirm the mechanism: serum tryptase drawn 30 minutes to 4 hours after an anaphylactic episode rises in true mast-cell-driven reactions; complement studies (C4, C1-INH antigen and function, C1q) distinguish hereditary and acquired bradykinin-mediated angioedema from histaminergic forms. Specific IgE testing (ImmunoCAP) and skin prick testing identify likely allergic triggers; oral food challenge under supervision remains the diagnostic standard when history is unclear. Recurrent isolated angioedema without urticaria and not responding to antihistamines must be assumed bradykinin-mediated until proven otherwise — testing C4 (low between attacks in HAE), C1-INH antigen, and C1-INH function is mandatory. Drug-induced angioedema is identified by stopping the offending agent and watching for resolution over weeks. Imaging is rarely needed except in suspected bowel-wall angioedema, where CT shows segmental wall thickening and ascites.
Allergic angioedema with an identified trigger has an excellent prognosis when avoidance is achievable: future episodes are largely preventable, and the standby auto-injector resolves accidental exposures in 70-80% with a single dose. Recurrent histaminergic angioedema with chronic urticaria is benign but persistent, with median duration of 1-5 years; spontaneous remission occurs in roughly 30-50% of patients within five years, and modern stepwise therapy controls symptoms in over 80% of treated individuals. Venom immunotherapy delivers durable protection in 95-98% of hymenoptera-allergic adults. Mortality from allergic angioedema is overwhelmingly driven by airway compromise: case-fatality is under 1% when adrenaline is given promptly and rises sharply when adrenaline is delayed or omitted. The most predictive risk factor for fatal outcome is asthma — uncontrolled asthma triples the risk of fatal anaphylaxis in food-triggered reactions and warrants intensified maintenance therapy.
Allergy and immunology referral is recommended after any episode of angioedema with airway involvement, systemic anaphylactic features, suspected drug allergy that limits future treatment options, or three or more attacks per year without an identified trigger. A specialist confirms the mechanism, performs skin and challenge testing safely, initiates omalizumab or venom immunotherapy, and creates a written emergency plan.
Find specialists →Acute episodes peak within 30 minutes to 2 hours and resolve over 24-72 hours with treatment. Hives accompanying the swelling clear within 6-24 hours. Bowel-wall swelling can take 48-72 hours to settle. Steroid-treated late-phase reactions resolve over 4-12 hours. Chronic forms typically respond to optimized therapy within 4-12 weeks; omalizumab benefit usually evident within 12 weeks.
Light to moderate aerobic exercise is safe between episodes and reduces stress-related flares. Patients with exercise-induced angioedema should avoid exercise within 2-4 hours of eating known co-triggers (especially wheat in WDEIA), carry an auto-injector when training, and exercise with a companion who knows the emergency plan.
Look for a board-certified allergist/immunologist with hospital affiliation for inpatient management of refractory or severe cases. Centers offering food and drug challenge testing, venom immunotherapy, and access to biologics such as omalizumab are best for recurrent or complex angioedema. Verify experience with both histaminergic and bradykinin-mediated forms.
Medically reviewed by AIHealz Medical Editorial Board · May 13, 2026
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