What can be causing my 14 ur old sons chest to hurt when he breaths in?

Possibly asthma: Esophagitis/spasm, gastritis, peptic ulcer disease, pancreatitis/gallbladder trouble, intestional spasm, as well as lung and heart, and chest wall (costochrondiritis) are common in adults. Your 11 y/o son with chest pain related to breathing could possibly be from asthma and chest wall inflammation...I suggest consult your/his doc for an eval and treatment. Best of luck.

Suspect stitch: Some folks, especially teens, experience folds in the pleura that lines the chest wall. This creates a knife-like pain ("stitch") on breathing in, relieved by inflating the lungs as much as possible. If this is the only symptom, it is harmless; should real shortness of breath or crushing chest pain occur, a physician's office visit at least is indicated.