Bleeding when the mouth is sucked hard may be caused by poor oral hygiene, usually gingivitis or periodontitis. Gingivitis is an inflammation of the gum margin, usually due to the stimulation of the gums by calculus and plaque, resulting in bleeding gums, which can usually subside after scaling and the gums can be restored to health. Periodontitis is generally due to the gum bleeding caused by subgingival calculus stimulating the gums, and is accompanied by the resorption of the alveolar bone and loss of gum attachment. Bleeding may also occur due to dental caries, food embedding, pressure on the gums and papillitis, which may also cause bleeding gums. It is necessary to remove the embedded food, apply local medicine, and fill the deeply decayed teeth or do inlay restoration to restore the adjacent relationship and occlusal relationship of the teeth, so that no more food will be embedded, and the gums can slowly recover health, and the commonly used medicine is iodine glycerin.