Is croup is an allergic reaction to airborne allergens?

Croup is not an allergic reaction to airborne allergens. It is a respiratory illness caused by a viral infection of the upper airway, specifically the trachea, larynx (voice box), and bronchial tubes. It is characterized by a barking cough, hoarseness, and difficulty breathing. While allergies can trigger asthma, which can cause similar symptoms to croup, croup itself is caused by a viral infection rather than an allergic reaction.