Lily starts coughing continuously whenever she helps her mother in dusting her room. It became so severe that she had to visit a doctor. What do you think is the cause of Lily's ailment? Why have all medications failed to treat her ailment?

It seems that Lily is allergic to dust. Dust allergy causes narrowing of the wind pipe and coughing. All other medications have failed because allergic cough cannot be treated with normal medicines. But medicines like Bronchodilators and steroids provide instant relief.