Asthma treatment is no longer one-size-fits-all. That’s because research is uncovering new asthma subtypes and treatments that can be tailored to each specific type. One subtype is eosinophilic asthma, or e-asthma, an often severe form of asthma marked by elevated levels of white blood cells called eosinophils.

“Asthma is characterized by airflow obstruction and limitation of airflow that’s associated with inflammation,” says Michael Wechsler, MD, MMSc, co-director of the Cohen Family Asthma Institute at National Jewish Health in Denver. “There’s a subset of asthma patients in whom that inflammation is caused by eosinophils.”

As we’re learning more about this specific subtype of asthma, it’s important to keep the facts straight. Here’s what we know so far.

1. Eosinophils play an important role in your immune system.

Eosinophils are part of your immune system and may play a critical role in your body’s defense against bacterial, viral, fungal, and parasitic infections, according to research published in April 2016 in Clinical Reviews in Allergy and Immunology. They help promote inflammation, your body’s protective response to injury and infection, but too many can cause excess inflammation and swelling. Elevated levels of eosinophils have been associated with asthma and other conditions, such as atopic dermatitis and leukemia.

2. Eosinophilic asthma often develops in adults.

Individuals who develop severe asthma in adulthood are more likely to have the eosinophilic type. The condition is most commonly diagnosed in adults 35 to 50, according to the American Partnership for Eosinophilic Disorders. “A large portion of people with severe adult-onset asthma have eosinophilia,” says Dr. Wechsler, “but you can have eosinophilic asthma starting at a young age as well.”

3. Up to half of cases of severe asthma may be associated with eosinophils.

The exact prevalence of eosinophilic asthma is unknown, but about 50 percent of people with severe asthma may have elevated levels of eosinophils in their blood and lungs, according to the National Heart, Lung, and Blood Institute. Your asthma may be considered severe if your symptoms interfere with daily activities, you use your rescue inhaler frequently, or your symptoms don’t respond to typical asthma treatments taken regularly and correctly.

4. A blood test can help diagnose eosinophilic asthma.

If you’re having trouble controlling asthma symptoms despite following your treatment plan, talk to your doctor or asthma specialist about getting tested for eosinophilic asthma. “It’s really important for people with severe asthma to ask, 'What kind of asthma do I have? Do I have eosinophils? What is the subtype of asthma?'” says Wechsler. New treatments released over the past three years can help with the eosinophilic subtype, says Wechsler.

A simple blood test called an eosinophil count can help diagnose eosinophilic asthma. Your doctor may also recommend a sputum eosinophil count or a bronchial biopsy to help confirm the diagnosis. “If you find out you have eosinophilic asthma, you should ask your doctor about potentially getting started on eosinophilic-specific therapies,” says Wechsler.

5. Other health conditions may impact eosinophilic asthma.

Additional testing could also help you feel better. “In people who have severe asthma with frequent flares, I do an extensive workup,” says Wechsler. “I’m trying to identify what type of asthma they have, but also I want to know: What are their comorbidities? What else is going on with them in regard to their asthma? Do they have bad reflux disease? Do they have bad sinus disease? Vocal cord dysfunction?” Addressing other health issues in parallel with asthma treatment may help you feel better.

6. Eosinophilic asthma is associated with nasal polyps.

People with eosinophilic asthma may have an increased risk of nasal polyps, or noncancerous growths inside the nose. A study published in March 2017 in Annals of Allergy, Asthma & Immunology showed that more patients with nasal polyps had eosinophilic asthma than a non-eosinophilic type. The study also found that those with eosinophilic asthma were more likely to have recurrent nasal polyps. “It’s likely that the same pathways that are involved in eosinophilic asthma are also involved in nasal polyps,” says Wechsler.

7. New medications are available to treat eosinophilic asthma.

Standard treatments for asthma include long-term controller medications and rescue medications that you use when your symptoms flare up. If these medications aren’t enough to control your asthma, your doctor may prescribe newer medications called biologics, which target specific molecules involved in the action of eosinophils to help lower eosinophil levels and reduce inflammation. Mepolizumab and reslizumab are antibodies against interleukin 5 (IL-5) molecules; benralizumab is an antibody against the IL-5-receptor-alpha-chain. These drugs are delivered by injection or infusion at your doctor's office. “This treatment doesn’t necessarily eliminate attacks or exacerbations, but in some people it does, and in other people it reduces them dramatically,” says Wechsler.

Talk to your doctor about the treatment plan that's right for you.