The causes of drooling when you smile usually include poor oral hygiene, anterior tooth malformation or nerve dysfunction, etc., which need to be treated promptly once discovered. Poor oral hygiene is mainly characterized by tartar plaque and dental caries, which can cause irritation to the oral cavity, and its accompanying inflammation will also promote salivary secretion, which inadvertently triggers the phenomenon of drooling; patients with malocclusion of anterior teeth due to the upper and lower teeth can not be completely closed, may also cause the phenomenon of drooling when you do open-mouth movements. In addition, nerve dysfunction, such as facial nerve palsy patients, the paralyzed side can appear the phenomenon of drooling, may be obvious when laughing. Repeatedly drooling when laughing should seek medical advice to clarify the cause.