🌿 Why Do Flare-Ups Happen Without an Obvious Infection?

Many people with asthma, ABPA (Allergic Bronchopulmonary Aspergillosis), or other eosinophilic lung conditions describe sudden “crashes” where they feel feverish, inflamed, and completely drained — even when tests don’t show an infection. This can be confusing and worrying, but there is a clear explanation.

🔬 The role of eosinophils

• Eosinophils are a type of white blood cell that drive allergic and inflammatory reactions.

• When too many become activated, they release chemicals and proteins that cause:

  • Inflammation in the airways and body

  • Fatigue and muscle aches

  • “Flu-like” symptoms

• In eosinophilic diseases such as ABPA, severe asthma, or EGPA, these episodes are often described as flare-ups.

🧩 Common triggers of flares

• Stress – both emotional and physical stress can tip the immune system into overdrive.

• Biologic not yet started – until a biologic (e.g. mepolizumab, benralizumab, tezepelumab) calms eosinophil activity, your immune system may stay “over-reactive.”

• Mechanical strain – back pain, muscle strain, or other physical problems can amplify inflammation.

• Minor viral infections – even a tiny cold virus, too mild to register on tests, can trigger eosinophil-driven inflammation.

📉 Why symptoms come and go

• Many patients feel very unwell at home (fever, aches, exhaustion), but by the time they see a doctor, their vital signs look normal again.

• This doesn’t mean the flare wasn’t real. Eosinophil flares often burn out quickly, leaving behind fatigue and soreness that can last for days.

⚠️ When to seek medical advice

Contact your healthcare team if you notice:

• Persistent or high fever

• Worsening shortness of breath

• New or increased cough

• Chest pain

These may signal an infection or another complication that needs treatment.

✅ Key message

Yes — high eosinophils can cause flare-ups that feel like sudden illness without infection. Many patients describe exactly this: sudden feverishness, inflammation, aches, and feeling “knocked flat” for a few days.

Biologic medicines are designed to reduce eosinophil activity, helping to cut down the number and severity of these flares.