We cough when sick because coughing is a protective reflex that helps clear the airways of irritants such as mucus, pathogens, and other secretions caused by infections. When we have a respiratory infection like a cold or flu, the inflammation and excess mucus production irritate sensory receptors in the airways, triggering the cough reflex to expel these irritants and keep the breathing passages clear. Additionally, the inflammatory response during sickness releases chemicals that stimulate nerve endings in the airways, further inducing coughing to help the body defend itself and maintain clear airways.
