Asthma vs ILO: How Are Their Breathing Symptoms Different?

When your rescue inhaler isn’t working and your throat feels tight, it is incredibly frustrating and frightening. While asthma most often causes chest tightness and difficulty breathing out, Inducible Laryngeal Obstruction (ILO)—sometimes called Vocal Cord Dysfunction (VCD)—typically causes throat tightness and difficulty breathing in ^[1][2]. Because these conditions affect different parts of the airway, asthma medications like bronchodilators do not open the throat in ILO ^[3][4]. However, it is very common to have both conditions at the same time ^[5].

Important Safety Warning: Do not try to self-diagnose ILO during an attack. A tight throat and a rescue inhaler that isn’t working can be signs of a life-threatening asthma attack, a severe allergic reaction (anaphylaxis), or another medical emergency ^[6][7]. Always follow your prescribed asthma action plan. Seek immediate emergency care if you have severe or rapidly worsening breathlessness, blue or gray lips, confusion, fainting, inability to speak in full sentences, facial swelling, or symptoms that do not improve promptly with your reliever medication. Never stop, reduce, or change your asthma medications without your doctor’s supervision.

Where the Obstruction Happens (and Terminology)

The fundamental difference between asthma and ILO is where the breathing problem occurs in your body:

• Asthma affects the lower airway. It causes inflammation and muscle spasms in the small tubes inside your lungs (the bronchi). This usually results in a feeling of chest tightness or a deep cough ^[2].
• ILO affects the upper airway. It occurs when the voice box (larynx) temporarily tightens and closes instead of opening when you breathe. This typically causes a sensation of throat tightness or a feeling like your voice is suddenly trapped ^[1][2]. You may hear this called Vocal Cord Dysfunction (VCD), but doctors increasingly prefer the broader term ILO because the obstruction can involve structures above the vocal cords as well.

Clues in Your Breathing

The way your breathing sounds and feels can provide clues to your care team, but these are general patterns, not absolute rules ^[8][2]. Diagnosis cannot be made from the direction of breathing alone.

• Asthma: People with asthma typically have more trouble breathing out (exhaling) ^[8]. It is frequently accompanied by a wheeze (a whistling sound coming from the chest).
• ILO: People with ILO often struggle more to breathe in (inhaling) ^[2][9]. Instead of a chest wheeze, they may have stridor, a harsh, gasping, or squeaking noise coming from the throat area ^[8][2].

Keep in mind that asthma can sometimes cause noisy breathing on the inhale, and ILO can sometimes affect the exhale.

Why Inhalers Do Not Work for ILO

Asthma rescue inhalers, such as short-acting bronchodilators, are designed to relax the lung muscles. Because ILO involves the muscles of the throat, asthma inhalers do not relieve ILO episodes ^[3][4].

However, if you have both conditions, your inhaler is still essential for treating the coexisting asthma. A non-working reliever should prompt a medical assessment, not a self-diagnosis. Relying on asthma inhalers for unrecognized ILO delays proper care and can lead to unnecessary prescriptions for oral steroids, which have significant side effects ^[4][5].

Different Triggers

While exercise can provoke both conditions, other triggers are more specific:

• Asthma triggers frequently include cold air, allergens (like pollen), smoke, and respiratory infections ^[10].
• ILO triggers often involve talking, shouting, singing, swallowing, strong odors, acid reflux, or stress ^[10][11]. (Note: Stress can trigger ILO physical reflexes; it does not mean your symptoms are imaginary or “just anxiety.”)

When exercise triggers ILO, the breathing difficulty typically peaks at maximum exertion and resolves rapidly once you stop moving, whereas exercise-induced asthma may take longer to peak and recover ^[11][9].

Diagnosis and Coexistence

Because ILO and mild asthma can look identical on baseline breathing tests like spirometry (a test measuring how much and how fast you can blow air out), standard tests alone cannot rule either condition out ^[12][2]. Asthma may require its own objective testing, such as spirometry before and after a bronchodilator.

The gold standard for diagnosing ILO is a flexible laryngoscopy, where a doctor uses a small camera to look directly at your vocal cords ^[13]. Because ILO is intermittent, your throat might look perfectly normal at rest ^[14]. Doctors often perform the laryngoscopy during a medically supervised provocation test to safely reproduce your symptoms. For example, Continuous Laryngoscopy during Exercise (CLE) is a specialized test used specifically for exercise-triggered symptoms ^[13][15].

Research shows these conditions frequently coexist. In specialty referral clinics, between 29% and 42% of patients tested had objective evidence of both asthma and ILO ^[2][5]. If you are diagnosed with ILO, treatment usually involves working with a Speech-Language Pathologist (SLP) to learn specialized breathing and throat-relaxation techniques, while your doctor continues to manage any coexisting asthma.