Coughs help your body clear your airways of irritants and prevent infection. But a deep cough from your chest may signal bronchitis or pneumonia. Although they may have different underlying causes, their symptoms can be similar—and both can be serious enough to send you to the doctor.

Bronchitis and pneumonia both involve inflammation in the chest. Both can cause coughs that bring up a slimy substance called phlegm to help clear out germs and pus. And both can cause shortness of breath and wheezing.

Bronchitis is a condition in which the bronchial tubes that lead to the lungs become inflamed. Viruses, bacteria, and even toxins like tobacco smoke can inflame the bronchial tubes. Most of the time, though, bronchitis is caused by an infection with one of several types of viruses. If you develop bronchitis during flu season, a likely culprit may be the flu virus. Cold viruses are also…