Acute allergic angioedema

Last updated Nov. 21, 2024, by Marisa Wexler, MS
Fact-checked by Joana Carvalho, PhD

Acute allergic angioedema refers to a form of angioedema that occurs as a result of an allergic reaction.

Like other angioedema types, it is marked by swelling in the deeper layers of the skin or in mucous membranes. However, swelling in this type is usually accompanied by hives and other allergy-related symptoms.

Acute allergic angioedema is the most common form of angioedema. It is usually treated by removing the agent that’s causing the allergy, alongside medications like antihistamines, corticosteroids, and epinephrine that can ease the underlying allergic reaction.

Causes and triggers

Acute allergic angioedema is caused by allergic reactions. In an allergic reaction, the body’s immune system mistakes a harmless substance for an infectious threat and launches an inflammatory attack against it. This inflammatory reaction ultimately drives allergy symptoms, which can include angioedema.

Allergic angioedema is a histaminergic form of angioedema, which means it’s driven by histamine, an inflammatory signaling molecule that’s released by immune cells during allergic reactions. This is the reason why antihistamines, which are medicines that work by blocking the effects of histamine, are a mainstay treatment for allergies.

The fact that swelling in allergic angioedema is driven mainly by histamine released during an allergic reaction sets this type of angioedema apart from other types of angioedema.

In hereditary angioedema, acquired angioedema, and nonallergic, or drug-induced angioedema, swelling is driven by a different signaling molecule called bradykinin. In idiopathic angioedema, swelling may be mediated by bradykinin, histamine, or other allergy mediators, but there is no clear trigger for the swelling attacks.

Substances that can trigger an allergic reaction are known as allergens, and virtually all of them can act as acute allergic angioedema causes. These allergens may include:

• certain foods or beverages, such as milk, eggs, shellfish, and nuts
• medications, such as antibiotics and nonsteroidal anti-inflammatory drugs
• contrast agents used in imaging tests
• latex
• venom from insect bites or stings
• pollen
• animal dander (scales or shed skin).

Symptoms

The defining symptom of allergic angioedema is swelling. As in other forms of angioedema, swelling most commonly occurs in the face, but it can also be observed in the neck, hands and feet, gut, and genitals.

While swelling doesn’t generally cause substantial problems, if it occurs in the throat or tongue, it can block the airways and make it difficult for a person to breathe, which is a medical emergency that requires immediate treatment.

The swelling in acute allergic angioedema is almost always accompanied by hives (urticaria), which are itchy, raised welts on the skin. These usually have an abnormal color, appearing reddish in people with pale skin or purplish in individuals with darker skin. Hives can vary greatly in size, from about the size of a pea to the size of a dinner plate. They can also have different shapes, appearing as circles, ovals, or elongated wormlike shapes.

Allergic angioedema is an acute form of angioedema, meaning that symptoms appear fairly quickly, usually within less than an hour or two after exposure to an allergen, and then disappear within a few days once the allergic reaction resolves. Symptoms generally do not recur, unless there is repeated exposure to an allergen that triggers a new allergic reaction. This sets allergic angioedema apart from forms of chronic angioedema, which are marked by periodic attacks of swelling.

In addition to swelling and hives, acute allergic angioedema symptoms often include other issues associated with allergic reactions, such as:

• wheezing
• runny nose
• red, watery eyes.

In severe cases, acute allergic angioedema may occur as part of anaphylaxis, which is a serious, potentially life-threatening allergic reaction whose symptoms may include:

• a rapid, weak pulse and low blood pressure
• wheezing and difficulty breathing
• nausea, vomiting, or diarrhea
• feeling dizzy or fainting.

Diagnosis

If a person is experiencing unexplained swelling, it’s generally recommended they seek medical attention. The swelling that characterizes angioedema is usually easy to identify, so doctors can typically tell when a person is experiencing angioedema from a physical examination.

The most challenging part of establishing an acute allergic angioedema diagnosis is confirming that swelling is being caused by an allergic reaction and pinpointing its exact trigger.

Usually, the first step in diagnosis is a detailed history where clinicians will ask patients about any potential allergens they may have been in contact with. They will also determine if the patient has any known history of allergic reactions, family history of angioedema, and other symptoms that may be occurring in addition to swelling. If allergy-like symptoms, such as a runny nose or hives, are also present, that can be a strong indicator of acute allergic angioedema.

To identify a trigger causing a patient’s allergic reaction, certain allergy tests may be performed, including:

• skin tests, where a small amount of the potential allergen is placed on the skin or injected under the skin to see if it triggers an allergic reaction
• blood tests, which measure the levels of specific antibodies, called immunoglobulin E, that are produced by immune cells in response to a specific allergen
• oral challenge test, where a patient ingests a small amount of a suspected food or medication under the supervision of a healthcare professional who can administer supportive care immediately if an allergic reaction occurs.

Treatment

The first and most important step for acute allergic angioedema treatment is removing the substance that is triggering the allergic reaction.

Other steps in treatment will depend on the severity and location of the swelling. Some cases may be mild enough that no specific treatment is required, while others may be life-threatening and require emergency care.

Emergency care is especially needed if a patient is having trouble breathing. In some cases, intubation may be necessary to keep the airways open to help patients breathe. In turn, if a patient is experiencing anaphylaxis, treatment with epinephrine, an injectable medication that’s the active agent in the Epi-Pen, should be given at once.

To get allergic reactions under control, antihistamines are usually the first line of treatment. Many different types of antihistamines are available, some over-the-counter, while others only with a prescription. Patients should talk to their healthcare providers about what type of antihistamine is most appropriate for their specific situation.

If antihistamines aren’t effective, a short course of corticosteroids, which are anti-inflammatory agents that powerfully suppress the immune system, may be used as an alternative medication for acute allergic angioedema.

Living with acute allergic angioedema

For people living with acute allergic angioedema, a key part of managing the condition is taking steps to avoid contact with known allergens. This will, of course, depend on the particular allergen.

For example, if a specific food or medication is the trigger, that substance should be avoided as much as possible. However, if airborne irritants, such as pollen, are responsible, it can be helpful to wear a mask or stay inside when pollen levels are high, and to equip one’s home with high-quality air filters.

Talking to an allergy specialist or a dietician is a good way to get guidance on how to avoid specific allergens.

Even with the best possible forethought and planning, allergic attacks can still sometimes happen, so it is important for people who have experienced acute allergic angioedema to have treatments on hand to manage future allergic reactions. This is particularly important for people who are at risk of anaphylaxis, for whom an Epi-Pen or comparable version of epinephrine should always be available in case it’s needed. It’s also recommended that people who carry epinephrine teach family members and friends how to administer it.

Managing allergies can sometimes be arduous and burdensome, so it’s also important to practice self-care and be willing to rely on others, including clinicians, friends, and family, for support and stress management.

Angioedema News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.