Hereditary angioedema (HAE) is treated with a combination of on-demand medications for acute swelling attacks and preventive therapies to reduce how often attacks occur. Unlike allergic reactions, HAE swelling does not respond to antihistamines, epinephrine, or corticosteroids, so having the right medications on hand is critical. Treatment has improved dramatically in the last decade, with newer preventive therapies reducing attack frequency by nearly 90%.
Why Standard Allergy Treatments Don’t Work
HAE is caused by a genetic mutation that leads to low levels or poor function of a protein called C1-inhibitor. This protein normally keeps a chain reaction in the blood in check. Without enough working C1-inhibitor, an enzyme called plasma kallikrein becomes overactive and produces excess bradykinin, a molecule that forces blood vessels to become leaky. Fluid seeps into surrounding tissue, causing the deep, painful swelling characteristic of HAE.
Because the swelling is driven by bradykinin rather than histamine, the medications used for allergic reactions simply target the wrong pathway. Every HAE treatment works by either replacing the missing C1-inhibitor protein, blocking kallikrein so less bradykinin is produced, or blocking the receptor that bradykinin binds to on blood vessel walls.
Treating Acute Attacks
When a swelling episode begins, the goal is to stop it as quickly as possible. Nearly all approved on-demand treatments require an injection, either under the skin or into a vein. No oral medication is currently approved for treating acute attacks.
The main options fall into three categories. C1-inhibitor replacement products deliver the protein your body is missing, directly restoring the brake on bradykinin production. These come in both plasma-derived and lab-made (recombinant) forms and are given intravenously. Icatibant is a self-injectable medication that blocks the bradykinin receptor on blood vessel walls, essentially preventing bradykinin from triggering swelling even though it’s still present. Ecallantide directly inhibits plasma kallikrein to shut down bradykinin production at its source.
All attacks involving the face, neck, or throat should be treated immediately. Throat swelling can block the airway and become life-threatening. Even after treatment, throat swelling can progress or return, so emergency medical care is essential any time the upper airway is involved. In severe cases, doctors may need to place a breathing tube or perform a surgical airway procedure early, before swelling closes off the throat entirely.
Abdominal attacks, while not immediately dangerous, can cause intense pain, nausea, and vomiting that mimics a surgical emergency. Treating these attacks early shortens their duration and reduces the chance of an emergency room visit.
Long-Term Prevention
Preventive therapy, called long-term prophylaxis, aims to reduce both the number and severity of attacks over time. Three first-line options are currently recommended.
- Subcutaneous C1-inhibitor (Haegarda): A self-injected replacement of the missing protein, given under the skin every three to four days. Approved for patients aged 6 and older.
- Lanadelumab (Takhzyro): A self-injected antibody that blocks plasma kallikrein, given every two to four weeks. Approved for patients 12 and older. In a long-term extension of its pivotal clinical trial, lanadelumab reduced the average attack rate by 87.4% compared to baseline. Many patients on the every-two-week schedule had zero or near-zero attacks.
- Berotralstat (Orladeyo): The only oral preventive option, taken as a single 150 mg capsule once daily with food. Approved for patients 12 and older. The most common side effects are gastrointestinal: abdominal pain, vomiting, diarrhea, and heartburn. These tend to be most noticeable in the first weeks and often improve over time.
The choice between these depends on how often you have attacks, your tolerance for injections, and how your body responds. Some people strongly prefer the convenience of a daily pill despite the stomach-related side effects, while others opt for less frequent injections that may offer greater attack reduction. Your specialist can help you weigh these tradeoffs.
Preparing for Surgery or Dental Work
Medical and dental procedures can trigger HAE attacks, particularly when they involve the mouth, throat, or airway. Short-term prophylaxis before a planned procedure significantly lowers that risk. The most common approach is an intravenous infusion of plasma-derived C1-inhibitor given one to three hours before the procedure. An older option, the androgen danazol, can be started five days before and continued for two days after, but it carries more side effects and is generally reserved for situations where C1-inhibitor products aren’t available.
Even with pre-procedure protection, you should have on-demand treatment accessible during and after the procedure in case breakthrough swelling occurs.
Treatment in Children
Children with HAE have fewer approved options, and the gap narrows as they get older. For kids under 12, the approved treatments include plasma-derived C1-inhibitor products for both acute attacks and prevention. Danazol is technically approved for prevention in all ages, but safety concerns, particularly effects on growth and hormones, limit its use in children.
Lanadelumab is approved starting at age 12, and clinical studies are evaluating its use in younger children aged 2 to 11, with dosing adjusted by age group. Berotralstat is also approved from age 12. For younger children, treatment plans center on C1-inhibitor replacement, and families are trained to recognize attacks early and administer treatment at home when possible.
Getting Diagnosed
If HAE is suspected, diagnosis typically starts with a blood test measuring complement C4 levels. A low C4 result is about 80% to 85% sensitive for detecting HAE and serves as a reliable screening tool. From there, doctors measure both the amount and the function of C1-inhibitor protein. In Type I HAE (the most common form), C1-inhibitor levels are simply too low. In Type II HAE, the protein is present in normal or even elevated amounts, but it doesn’t work properly. Confirming the diagnosis sometimes requires genetic testing for mutations in the SERPING1 gene.
Because HAE is rare and its symptoms overlap with allergic angioedema and other conditions, many people go years before receiving the correct diagnosis. A family history of unexplained swelling episodes is one of the strongest clues. If you have a first-degree relative with HAE, screening is worthwhile even if you haven’t had symptoms yet, since attacks can begin at any age.
Living With HAE Between Attacks
Beyond medications, managing HAE means having a reliable plan for when attacks happen. Most specialists recommend keeping at least two doses of on-demand treatment at home at all times, carrying medication when traveling, and wearing medical identification that specifies the diagnosis and notes that standard allergy treatments are ineffective.
Stress, infections, hormonal changes, and physical trauma are common attack triggers, though many episodes have no identifiable cause. Tracking attacks in a diary, including their location, severity, and any possible triggers, helps your specialist fine-tune your preventive regimen over time. The goal of modern HAE management is not just surviving attacks but reducing them to the point where the condition no longer dictates your daily life.