Hereditary Angioedema (HAE)

Written by Marijke Vroomen Durning, RN
Medically Reviewed by Neha Pathak, MD on December 04, 2025
10 min read

Hereditary angioedema (HAE) is a rare genetic condition that causes swelling under the skin and lining of your gut and lungs. “Angio” means it affects your blood vessels. “Edema” means swelling. So when you have HAE your blood vessels swell and cause fluid to leak into your surrounding tissues. It can happen in different parts of your body. 

 

 

HAE is something you’re born with. But it can take time to get diagnosed even after you start noticing symptoms. Although you’ll always have it, treatment can help you manage and prevent attacks. 

There have been big improvements in HAE treatment, and researchers continue to look for new solutions. So your options and outlook with HAE are much better today than they were in the past. The key is to get the right diagnosis and treatment.

The cause of your HAE depends on which type you have. In type I HAE, you’ll have too little of a protein called C1 inhibitor in your body. This protein normally helps control swelling. When you don’t have enough, tiny blood vessels can push fluid into nearby tissues. As fluid builds up in your tissues, it can lead to episodes of sudden swelling. 

 

With type II HAE, you have the C1 inhibitor. But for some reason, it doesn’t work right. This also results in attacks of swelling.

The third type of HAE has similar symptoms, but it’s not caused by C1-INH deficiency or the C1 inhibitor protein not working as it should. Researchers aren’t sure about the cause, but they believe there’s a change in some genes that might be responsible. The gene change happens for unknown reasons, and if you have the broken gene, you can pass it on to your children. Scientists are trying to understand this HAE type better.

The main HAE symptom is swelling, much like hives. The difference is hives pop up above the skin, while angioedema swelling is below the skin. You won’t have the itching or hives that people often get with allergic reactions. A bout may last two to five days. And unlike hives, angioedema swelling isn’t usually itchy.

Swelling in the throat is the most dangerous symptom because it can affect your breathing. This is an emergency. Call 911 if you or someone else is having a hard time breathing.

Puffiness in the feet and hands can be painful and make it hard to go about your daily life.

Swelling in your belly can cause:

  • Cramping or pain
  • Nausea
  • Vomiting
  • Diarrhea
  • Dehydration
  • In severe cases, shock

You could also have a skin rash.

You may notice warning signs before swelling begins. These may include:

  • Extreme fatigue
  • Muscle aches
  • Tingling
  • Headache
  • Belly pain
  • Hoarseness
  • Mood changes

Symptoms of HAE most often start in childhood and get worse during the teen years. However, many people don't know they have HAE. You may have swelling and symptoms without a diagnosis until you’re an adult. 

HAE symptoms can vary a lot. How often the bouts of swelling happen, how strong they are, and where you have HAE on or in your body are different for everyone. The attacks can come and go. They also can move to different spots, even during the same episode. The swelling typically goes away on its own but can also be a life-threatening event.

The frequency of your attacks can vary a lot, too. You may have attacks as often as every one to two weeks. Or you may only have them once or twice a year. Either way, HAE attacks can be tough to manage especially if you don’t have the right treatment and plan in place.

Although you may not be able to tell what your triggers are, common ones include:

  • Stress or anxiety
  • Minor injury or surgery
  • Illnesses such as colds or the flu
  • Infections
  • Physical activities such as typing, hammering, or pushing a lawn mower
  • Medications, including some used for high blood pressure and congestive heart failure

Hormones can also trigger episodes. Women may notice a difference in the number or sharpness of attacks when they:

  • Have their period
  • Are pregnant. For some women, it doesn't happen as often when they’re pregnant, but then the attacks come back after they give birth.
  • Use birth control or hormone replacement therapy containing estrogen. Women usually say they have more and worse attacks while on these medicines.

The right diagnosis is key. Sometimes, people are treated for allergies when it's really HAE that causes their swelling. Antihistamines and corticosteroids that treat allergies don’t work well for this disease.

You can have severe stomach swelling, pain, diarrhea, and severe dehydration. And if misdiagnosed, it can lead to surgery you don't need.

Your doctor will do a physical exam. You'll need blood tests to confirm that it’s HAE and to rule out other possible causes. The blood tests for HAE are:

  • C1 inhibitor function
  • C1 inhibitor level
  • Complement component 4 (may be normal if you’re not having an episode and only changing when you are having one)

Your doctor may also recommend genetic testing to see if you have genetic changes (mutations) that cause the condition.

If you do have HAE, ask your doctor to refer you to a specialist familiar with the condition. You should also ask your doctor about having other members of your family tested, even if no one has symptoms.

It’s overwhelming to get a diagnosis of a rare chronic condition like HAE. But it may also be a relief in some ways. Now you have some answers about your symptoms and what’s to come. You can get the right treatment to manage your attacks. It’s always a good idea to ask questions to make sure you understand your disease and how to manage it as best you can.

 

Because hereditary angioedema is rare, it can be challenging to find a specialist who is experienced in managing it. But there are resources available to help.

The U.S. Hereditary Angioedema Association helps people who have HAE and their caregivers. The organization has a form on its site that you can fill out and a health advocate will reach out to you. 

Other ways you can look for experts include:

  • Reaching out to major academic medical centers that have angioedema and allergy programs
  • Meeting with a board-certified allergist or immunologist to see if they have experience treating HAE or if they know someone they can refer you to

HAE complications will depend on the location and severity of your symptoms. For example, the most serious complication is a blockage of the airway if your throat or tongue gets too swollen. This is a medical emergency.

You may also be unable to do certain activities because of severe pain. This could mean missing school, work, and fun activities. 

Swelling and pain in your belly could result in nausea, vomiting, and diarrhea. These GI symptoms could lead to dehydration if you can’t keep fluids in or you lose too much. Talk to your care team about complications to watch for and when you should call them right away. Having a plan in place in the event of an emergency is key.

Learn as much as you can about HAE so you can make informed decisions about your treatment and any medications you should be cautious with. If you can figure out your triggers, you can better avoid them. It may help to track your attacks and symptoms in a journal and look for patterns.

Talk to your doctor before you have any dental work or other medical procedures. They may want you to take medication to avoid a flare. Also talk with your doctor before you take any new prescription medicines. There’s a chance certain medicines could trigger an attack. Any medical professional who treats you should know about your HAE and what to do in case of an episode. Carry your medical information and on-demand medicines with you at all times.

Make sure all caregivers, family members, and close friends or co-workers know about the condition and what to do if an attack happens. If your child has HAE, note any changes in behavior before an attack. As they get older, they'll need to learn their triggers, warning signs, and treatment needs. 

Remember: Any swelling in the throat is an emergency. Take your medication for attacks and call 911.

There's no cure for HAE, but new treatments have made it possible to manage the symptoms and enjoy an active life. Before doctors had medicines to treat and prevent HAE episodes, about 1 in 4 people with HAE died from it. Today, you can expect to live a normal life span.

The biggest risk today is having HAE without knowing it. HAE can be life-threatening when the swelling causes difficulty breathing or choking. Undiagnosed HAE comes with the greatest risk because you won’t have the proper treatment available. 

Misdiagnosis is another serious issue when you have undiagnosed HAE. You may receive the wrong treatment — including surgery — for severe abdominal pain. 

Connect with others who are living with HAE. They can share their insights and tips to help you manage your symptoms. To learn more about HAE and to find the support of others who have it, visit the U.S. Hereditary Angioedema Association at www.haea.org.

Caring for your emotional health

Living with a disease that can be uncomfortable, painful, unpredictable, and life-threatening is hard on your emotional and mental health. You might be nervous about participating in activities or worry every time you get sick or you start feeling symptoms again. 

Just as it’s important to take care of the physical problems caused by your HAE, it’s important to take care of yourself emotionally. This means reaching out for help when you need it, either through the Hereditary Angioedema Association, your primary care doctor, or your HAE care team. Consider making an appointment to speak with a counselor or therapist who works with people who have chronic illnesses. Asking for help from friends and family members is also key. You don’t have to go through this alone.

Caring for someone with HAE can be stressful because you never know when another episode may happen. The Hereditary Angioedema Association has resources for caregivers, including parents of children with HAE. You can also ask your child’s doctor if there are local resources or other parents who you might reach out to, so you don’t feel alone.

Hereditary angioedema is a genetic disease that has no cure, but treatments can manage symptoms and reduce the risk of episodes. It’s very important that the people around you know about your HAE so if you start to experience swelling, especially in your mouth and throat, they know what to do. Most people with HAE go on to live full and long lives. The Hereditary Angioedema Association can offer you resources and support so you don’t feel alone.

How common is HAE?

Hereditary angioedema is a rare condition. It affects fewer than 7,000 people in the U.S.

How does HAE develop?

HAE is a genetic disease, which means you’re born with it. The symptoms may not show up for years though. It often takes much longer to get a diagnosis.

What triggers a hereditary angioedema episode?

HAE episodes can appear out of nowhere, but some people have specific triggers, such as an infection or illness, an injury, or even hormonal issues, like having your period. Consider keeping a journal to see if you can identify your triggers.

Is there a cure for hereditary angioedema?

No. There’s no cure for this genetic disease, but there are medications that can help reduce the swelling from an episode and reduce your risk of future ones.

Can I travel if I have HAE?

Yes. Traveling with HAE takes planning. It’s important to know that you can get any needed treatment during your trip if you have an episode. Talk to your doctor in advance about how you can travel safely.