There is no denying that laughter is indeed the best medicine as we feel really light after a good, hearty laugh. We have all had moments in life, where we laughed so hard that our jaw started hurting and we had to hold our stomach to ease the pain.But who knew that laughing your heart out could also turn into a really painful situation? In a strange incident, a Chinese woman was left with her mouth wide open (literally) after a good bout of laughter. This disastrous incident took place when the woman was travelling on a high-speed train to Guangzhou in South China.Several reports state that this extremely weird event took place in China's Guangdong province, where a lot of passengers noticed a woman laughing uncontrollably for several minutes. However, as soon as she finished laughing, she realised that her jaw had been dislocated and her mouth was left wide open.Luckily, there was a doctor on board who stepped forward to help the woman in distress. According to reports, Doctor Luo Wensheng of Liwan Hospital had boarded the train, after an urgent appeal for medical assistance was broadcast on the train.Talking about the unfortunate incident, Doctor Wensheng said, “I rushed over and found the passenger unable to speak or close her mouth. She was drooling, so I initially thought she had had a stroke. But I took her blood pressure.”While he was able to reset her jaw, he did warn her that he wasn’t an expert and things might go south. “I warned her that I wasn't an expert, but I knew how to do the procedure. I also told her there was a chance I wouldn't be able to set it.”The passenger revealed to the doctor that she had dislocated her jaw in the past due to repeated vomiting during pregnancy. To this, the doctor added, “If you've dislocated your jaw in the past, laughing, yawning or even just opening your mouth too wide can lead to it happening again.”While she was lucky enough to have a doctor on board to treat her, the cause behind the fit of laughter is still is a mystery.