Severe asthma may be eosinophilic asthma. About 50% of people with severe asthma have too many eosinophils in their lungs. Eosinophils are white blood cells, which are a normal part of the immune system. Eosinophils can cause airway inflammation for some people with severe asthma, which can lead to asthma symptoms and attacks.

A simple blood test can help determine if you have eosinophilic asthma.

The impact of eosinophils on severe asthma

Potential health risks of eosinophilic asthma

When eosinophilic asthma is uncontrolled, patients can have:

Greater risk for future asthma attacks

Worse lung function, making it harder to breathe

Repeated use of oral steroids like prednisone

What you need to know about oral steroids

Oral steroids like prednisone are used to treat asthma attacks and may control severe asthma. There are several health risks that can occur with long-term use:

  • Glaucoma
  • Heart conditions
  • Weight gain
  • Diabetes
  • Osteoporosis

Even occasional doses can increase the risk for stomach ulcers, bone fractures, and high blood pressure.

Eosinophilic asthma can be treated by an asthma specialist

An allergist or a pulmonologist can treat eosinophilic asthma. Here’s how to work with an asthma specialist:


Request a referral from your primary care physician to see a specialist.


Discuss your asthma symptoms at your first asthma specialist appointment.Download discussion guide.


Take this checklist to your next appointment with your asthma specialist, so you can both decide if FASENRA may be right for you

Check the box(es) below if you have:

  Used rescue inhalers more than 2 days per week to control your asthma symptoms
  Taken oral steroids like prednisone for your asthma in the last 12 months
  Experienced an asthma attack that required emergency room medical care in last 12 months

What are your current asthma medications and how often do you take them?


The discussion guide will include questions for your asthma specialist, like "Could eosinophils be a cause of my asthma?"

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A simple blood test measures your eosinophil count. Elevated eosinophils may indicate eosinophilic asthma.

Important Safety Information

Do not receive FASENRA if you are allergic to benralizumab or any of the ingredients in FASENRA. Do not use to treat sudden breathing problems.

FASENRA may cause serious side effects, including:

  • allergic (hypersensitivity) reactions, including anaphylaxis. Serious allergic reactions can happen after you get your FASENRA injection. Allergic reactions can sometimes happen hours or days after you get your injection. Tell your healthcare provider or get emergency help right away if you have any of the following symptoms of an allergic reaction:
    • swelling of your face, mouth and tongue
    • breathing problems
    • fainting, dizziness, feeling lightheaded (low blood pressure)
    • rash
    • hives

Before receiving FASENRA, tell your healthcare provider about all of your medical conditions, including if you:

  • are taking oral or inhaled corticosteroid medicines. Do not stop taking your corticosteroid medicines unless instructed by your healthcare provider. This may cause other symptoms that were controlled by the corticosteroid medicine to come back.
  • have a parasitic (helminth) infection.
  • are pregnant or plan to become pregnant. It is not known if FASENRA will harm your unborn baby. Tell your healthcare provider if you become pregnant during your treatment with FASENRA.
  • are breastfeeding or plan to breastfeed. It is not known if FASENRA passes into your breast milk. Talk to your healthcare provider about the best way to feed your baby if you receive FASENRA.
  • are taking prescription and over-the-counter medicines, vitamins, or herbal supplements.

Do not stop taking your other asthma medicines unless instructed to do so by your healthcare provider.

The most common side effects of FASENRA include: headache and sore throat. These are not all the possible side effects of FASENRA.


FASENRA is a prescription medicine used with other asthma medicines for the maintenance treatment of asthma in people 12 years and older whose asthma is not controlled with their current asthma medicines. FASENRA helps prevent severe asthma attacks (exacerbations) and may improve your breathing. Medicines such as FASENRA reduce blood eosinophils. Eosinophils are a type of white blood cell that may contribute to your asthma.

FASENRA is not used to treat other problems caused by eosinophils and is not used to treat sudden breathing problems. Tell your health care provider if your asthma does not get better or if it gets worse after you start treatment with FASENRA.

It is not known if FASENRA is safe and effective in children under 12 years of age.

Please see full Prescribing Information including Patient Information for FASENRA.

You may report side effects related to AstraZeneca products by clicking here.