How can coughing protect the body during illness?

In the context of Darwinian medicine, coughing is understood not as a disease itself, but as a protective reflex shaped by natural selection to defend the body.1

Coughing serves as an essential defense mechanism by forcefully expelling air from the lungs to clear the respiratory tract of excessive secretions, mucus, or foreign materials. By removing these irritants, the body prevents complications such as pneumonia, which can occur if an effective cough reflex is lost due to injury or disease.23

Because coughing is a functional defense, it is often categorized under the "smoke-detector principle." Much like a sensitive smoke detector may trigger a false alarm to ensure a fire is never missed, the body may express a cough even when the threat is minor, because the cost of failing to express a necessary defense is far greater than the nuisance of the reflex itself. Consequently, medical experts advise that a productive cough—one that successfully clears secretions—should generally not be suppressed.13