What causes angioneurotic oedema?

The timing, accompanying symptoms and medicine history help separate these possibilities. Whatever the suspected cause, swelling that interferes with breathing or swallowing is an emergency.

Allergic angioedema is driven by histamine and may appear with itchy hives after exposure to a food, medicine, insect sting or another trigger. Infections can sometimes accompany an episode. A separate pathway involving bradykinin may be inherited, acquired, or associated with certain medicines used for blood pressure.

Bradykinin-related attacks often occur without hives and can involve the face, limbs, genitals, bowel or airway. Some people have spontaneous episodes in which no definite trigger is found. Similar-looking swelling may also arise from local inflammation, so examination matters.

Write down when the swelling began, how quickly it developed, where it appeared and whether there was itching, hives, abdominal pain or breathing difficulty. Record recent foods, stings, illnesses, dental work and every prescription, non-prescription medicine and supplement. A photograph can help if the swelling fades before an appointment.

Tell the clinician about relatives with unexplained swelling or severe abdominal attacks. Do not deliberately expose yourself again to a suspected trigger, and do not change essential medication without medical guidance. The assessment may lead to allergy review, medication changes or testing for an inherited mechanism.

Get emergency help for swelling of the tongue or throat, breathing difficulty, a hoarse or changing voice, trouble swallowing, faintness or rapid progression. Prompt assessment is also appropriate for repeated attacks, severe unexplained abdominal pain with swelling, or symptoms beginning after a newly started medicine. Urgency depends on the symptoms and sites involved, not on whether a cause seems common.

Ask which mechanism fits your pattern, whether any current medicine could contribute, what testing is useful, and what to do if swelling returns. If an inherited form is considered, ask whether family members should seek advice and how an emergency plan should be shared with schools, workplaces or travel companions.