There are many causes of yellow granules in the mouth, such as sebaceous gland ectasia, tonsil stones, oral herpes and so on. 1. Sebaceous gland ectasia: small yellow particles in the mouth need to be considered as sebaceous gland ectasia, usually no discomfort symptoms, occurring on both sides of the parotid gland around the nipple, upper and lower inner side of the lips and other locations, the overall surface is smooth, the texture is relatively soft. 2. Tonsil stones: yellow particles in the mouth may also be tonsil stones, due to tonsillitis caused by food debris into the tonsil crypt location, wrapped in bacteria, long after the formation of yellow particles. 3. Oral herpes: Oral herpes is a viral infection that can cause the formation of herpes in the oral cavity, which may show the phenomenon of yellow particles in the mouth in the early stages, and later breakouts will occur, accompanied by pain. There are many reasons for the yellow particles in the mouth, after the appearance of symptoms, it is recommended to go to the hospital in a timely manner to improve the examination, under the guidance of the doctor to take standardized treatment, do not ignore the symptoms, to take it lightly.