Acute allergic angioedema is an acute but temporary swelling of the skin caused by an allergic reaction. Skin and mucus membranes of the lips and around the eyes are most often affected, but swelling can also occur in the lining of the throat and mouth.

This allergen-triggered form of angioedema is almost always accompanied by hives and other signs of an allergic reaction. It occurs relatively quickly, with swellings peaking in size one to two hours after onset.

How severe is acute allergic angioedema?

The severity of acute allergic angioedema varies depending on the location and speed of the swellings.

Anaphylactic shock, a sudden drop in blood pressure and constriction of the throat due to a severe allergic reaction, is of major concern in this form of angioedema and emergency treatment is essential. Anaphylaxis usually occurs quickly, within minutes of a reaction to an allergen, and is caused by immune system releasing a flood of chemicals that induce rapid swelling to the mouth, throat and neck, narrowing airways and lowering blood pressure.

Other symptoms of anaphylactic shock can include hives or flush/very pale skin, a weak and rapid pulse, and dizziness, fainting, or collapse.

More often, however, cases of acute allergic angioedema are mild and localized to areas, such as the lips or eyes, and are not life-threatening. The swellings can be painful and tender, but may not be itchy.

What triggers acute allergic angioedema?

Acute allergic angioedema is an allergic reaction that can be triggered by a range of allergens. Common triggers include foods such as nuts, shellfish, milk, and eggs, and insect stings or bites.

Some medicines can also trigger this type of reaction. These include:

Some vaccines may also cause allergic reactions with angioedema.

The swelling reaction typically occurs shortly after exposure to the allergen, and can be triggered by the same allergen again  at a later date.

How is acute allergic angioedema treated?

Acute allergic angioedema swellings generally do not last more than 48-72 hours (about three days.) In the early hours of the reaction, when there is the highest risk for the swelling to become problematic or life-threatening, acute allergic angioedema can be treated with such allergy medications as antihistamines, corticosteroids, and epinephrine. Cases of anaphylaxis, when a person is in shock or going into shock, require emergency medical attention.

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