Chest pain when laughing may be caused by strenuous exercise, chest trauma, pleurisy and other factors. 1. Strenuous exercise: If you have recently engaged in strenuous exercise, it may lead to the accumulation of a large amount of lactic acid in the chest muscles, and when a person laughs, it may lead to the contraction of the chest muscles, thus causing pain. 2. Chest trauma: If the chest is accidentally hit, it may lead to soft tissue contusion, swelling and pain symptoms, and the pain symptoms may be more obvious when laughing. 3. Pleurisy: If the pleura is infected and inflammation is triggered, symptoms of chest pain may appear, which is usually manifested as a sudden stabbing pain, and deep breathing, laughing, coughing, sneezing, etc. may cause chest pain to worsen. There are many other reasons that can lead to chest pain when laughing, if there is no strenuous exercise, and the chest is not impacted, it is recommended that the patient consult a doctor in a timely manner to clarify the diagnosis, so as not to delay the condition.