When you live with both hereditary angioedema (HAE) and asthma, sudden trouble breathing can make it hard to tell which condition is responsible. Although both conditions can affect breathing, they do it in different ways. Some triggers or symptoms may overlap, which can make flares harder to sort out.

Compared with the general population, people with HAE may be more likely to have asthma. One Canadian survey found about 17 percent of people with HAE also have asthma, compared with roughly 8 percent to 11 percent of people without HAE. Other studies have found similar patterns.

Here’s what you need to know about the differences and similarities between HAE and asthma and how they can affect each other and your day-to-day life.

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How Do HAE and Asthma Symptoms Compare?

Here’s how the symptoms stack up, starting with the breathing issues.

Airway and Breathing Symptoms

Hereditary angioedema can cause swelling in your upper airway — your throat and voice box, also called the larynx. This kind of attack is rare, accounting for only 1 percent to 3 percent of HAE attacks, but it’s the most serious kind.

Upper airway swelling from HAE can become life-threatening if it isn’t treated quickly because it can block your airway.

Symptoms of upper airway swelling from HAE can include:

• Shortness of breath
• Trouble swallowing
• A change in your voice
• A gasping or high-pitched sound when you breathe in

About half of people with HAE will experience this type of attack at some point in their lives, even though it’s uncommon among all HAE attacks.

Asthma affects a different part of your airway — the bronchial tubes deep inside your lungs.

Common symptoms of asthma include:

• Wheezing
• Coughing
• Chest tightness
• Shortness of breath
• Difficulty breathing out

Triggers like cold air, exercise, or pollen can bring on an asthma flare. A severe or uncontrolled asthma attack can also become life-threatening.

Other Common HAE Symptoms

Most HAE attacks don’t involve the airway. Swelling more often shows up in the hands, feet, face, or genitals, and it can also affect your gastrointestinal (GI or digestive) tract.

A GI attack can cause abdominal pain, nausea, vomiting, and diarrhea. These symptoms may be intense, but they generally aren’t life-threatening in the same way airway swelling can be.

When Symptoms Usually Start

Both conditions often appear early in life. About half of people with the most common types of HAE notice symptoms by age 10. One survey found that the average age of first symptoms was around 17.

Asthma also commonly starts in childhood, and many children with asthma first experience symptoms by age 6. The two conditions can be hard to tell apart in younger children.

As children grow, the two conditions can take different paths. HAE symptoms often become more intense around puberty, while children with asthma may have fewer symptoms as they get older and their airways grow. However, asthma symptoms can also continue or come back later.

What Causes HAE and Asthma?

Both HAE and asthma involve immune-related pathways, but in different ways.

The Immune System Connection

Asthma often involves an allergic immune pathway, including histamine from mast cells (immune cells involved in allergic reactions) and immunoglobulin E (IgE), an antibody involved in many allergic reactions.

In the most common types of HAE, type 1 HAE and type 2 HAE, swelling works through a different, nonallergic pathway involving a protein called C1 inhibitor (C1INH) and a substance called bradykinin.

Because HAE’s swelling is driven by different immune proteins, asthma and allergy medications such as antihistamines, corticosteroids, and epinephrine don’t work on HAE attacks. If you have both conditions, your allergist or HAE specialist can walk you through when to use which type of medication.

Genetics, Allergies, and Shared Triggers

Many cases of asthma are allergic, triggered by allergens like pollen or pet dander. Asthma can run in families, but it’s generally thought to result from a mix of genetic risk and environmental factors.

HAE is different. The most common types of HAE are linked to mutations (variations) in the SERPING1 gene and aren’t considered allergies, even though the timing of attacks can sometimes appear that way.

Many factors can trigger HAE swelling episodes. Common examples include:

• Physical trauma
• Dental work
• Infections
• Emotional stress

There also appears to be a seasonal connection. In some cases, there may be no clear trigger.

One study found that nearly 40 percent of people with type 1 or type 2 HAE reported more frequent attacks during pollen season (between March and October), whether or not they had a pollen allergy. Findings like this highlight the complex biology of HAE.

How Can Having Both HAE and Asthma Affect You?

Here’s what having both HAE and asthma can mean for your day-to-day life.

Difficulty Identifying Which Condition Is Causing Symptoms

Because both conditions can cause breathing trouble, it’s not unusual for one to be mistaken for the other. This is especially true in children, where upper airway swelling from HAE can be misdiagnosed as asthma or other throat problems.

Telling the two apart in the moment can be challenging, even for experienced doctors. In one case report, a woman diagnosed with HAE was hospitalized for what looked like a combined asthma and HAE attack. Blood tests during that episode suggested the swelling was actually a separate allergic reaction rather than a true HAE attack.

While that’s a single case, not a general rule, it shows that HAE, asthma, and allergic reactions can sometimes be difficult to tell apart.

Can One Condition Set Off the Other?

Having both conditions can sometimes feel like a domino effect. Stress is a known trigger for HAE attacks, and stress can also worsen asthma, so a hard week, or the strain of managing one flare, may leave you more vulnerable to the other.

In some cases, the connection may look more direct. One study found that about 1 in 6 people with type 1 or type 2 HAE who also had allergic sensitivities experienced an HAE attack that seemed to be triggered by immune activation during an allergic reaction.

That doesn’t happen to everyone, and the study wasn’t conclusive. But it’s worth tracking if you notice your symptoms tend to cluster together.

Make a Plan for Symptoms and Emergencies

Whether you have HAE, asthma, or both, having a plan in place can help you act quickly when symptoms start. A clear plan may also help reduce the risk of dangerous outcomes during a breathing emergency.

A practical first step is keeping a simple symptom log. Noting whether an episode feels like throat tightness or chest wheezing, along with possible triggers, gives you and your doctor valuable clarity over time.

Have an action plan for both HAE and asthma, clearly noting which symptoms call for which treatment. This way, care providers have the information they need during an emergency.

For peace of mind, keep your HAE on-demand medication and asthma rescue inhaler available as directed by your doctor.

Finally, talk to your allergist or HAE specialist about your combined action plan. Having a clear guide for specific symptoms can help you know which treatment to use and when to seek emergency help.

Join the Conversation

On myHAEteam, people share their experiences with hereditary angioedema, get advice, and find support from others who understand.

Have you noticed any patterns between your asthma symptoms and HAE attacks? Share your experience in the comments below.