What Is Eosinophilic Asthma?

Medically Reviewed by Carol DerSarkissian, MD on March 20, 2024
3 min read

For a long time, doctors thought of asthma as just one disease. But they now realize there’s more to the story. They’ve started to think of asthma like a collection of conditions, with differences such as what age you start to have it, what symptoms you get, and how to best treat it.

That’s where eosinophilic asthma comes in. It’s what doctors call a subtype of asthma. Researchers are still working out how to define these subtypes, and it’s important work because it may lead to different, more effective treatments.

Until very recently, eosinophilic asthma meant more frequent asthma attacks and a lower quality of life. But an understanding of subtypes has led to new medicines that are quickly changing that picture.

Eosinophilic asthma is a rare type of asthma. It’s often severe and usually comes on in adults. The main treatment for asthma -- drugs called inhaled corticosteroids -- don’t have much of an effect on it, even in high doses. That means it's harder to manage and you’re more likely to have asthma attacks. Usually, you need to take corticosteroid pills, which can have more side effects than an inhaler. Several biologics are approved to reduce the frequency of eosinophilic asthma attacks. These include:

Your respiratory system is your body’s system for breathing. It goes from your nose and mouth down to the tiniest airways in your lungs. When you have eosinophilic asthma, you have inflammation in your respiratory system caused by cells called eosinophils.

Eosinophils are white blood cells. They’re part of your body’s immune system, and normally, they help you fight disease. One of their jobs is to help cause swelling. That may sound odd, but swelling is one of your body’s key tools in fighting germs. But too much swelling can cause problems.

More and more, doctors are coming to see that there's really no such thing as “regular asthma.” But something like classic, childhood asthma may look like this:

  • Comes on when you’re a kid
  • Often gets triggered by an allergen, like pet dander or dust mites
  • Causes swelling in the airways, and symptoms like wheezing and trouble breathing
  • Responds well to treatment with inhaled corticosteroids

When you look at eosinophilic asthma, it:

  • Tends to come on in adults
  • Isn’t usually caused by allergies -- people who get it tend not to have allergies
  • Causes swelling in your entire respiratory system
  • May not seem like asthma at first because the main symptom may involve shortness of breath rather than wheezing
  • Doesn’t respond well to inhaled corticosteroids, even at high doses

Doctors don’t actually know what causes eosinophilic asthma. There also aren’t any clear things, like foods or amount of exercise, that make you more likely to get it.

What they do know is that it usually comes on in adults ages 35-50 with no allergies. Sometimes it happens in older adults, and kids can get it too, but that’s not as common. And while adult asthma usually affects more women than men, eosinophilic asthma affects them at about the same rate.