A severe cough lasting for two days may be caused by a viral infection, allergies, or airway irritation. Corticosteroids such as Defcort (Deflazacort) may take several hours to show an effect and should be used only under medical supervision. Supportive measures include adequate hydration, rest, and avoiding irritants. Seek medical attention immediately if the cough worsens, persists beyond a few days, or is accompanied by fever, shortness of breath, or chest pain.