There are many reasons why the left side of the rib cage hurts when you inhale, and there are several common reasons why the left side of the rib cage hurts when you inhale: first, it may be caused by a fracture, and if it is caused by a fracture, in addition to the pain when inhaling, it will also be accompanied by symptoms of restricted activity. Second, it may be caused by pneumothorax, if it is caused by pneumothorax, in addition to pain under the ribs when inhaling, it will also be accompanied by irritating cough and hemoptysis, if it is caused by pneumothorax, the rib pain when inhaling should be taken for examination, if the condition is not serious, it can recover by itself through a period of rest, during this period, we should pay attention to avoid excessive emotional excitement and no strenuous activities, if If the condition is serious, surgery should be considered. There is also the possibility of rib neuritis, which should be treated with oral non-steroidal anti-inflammatory and analgesic drugs and neurotrophic drugs.