It is likely that the inability to induce vomiting and only saliva is due to the fact that the induction of vomiting is not strong enough and the stimulation of the stomach is relatively small, thus causing the phenomenon of vomiting with only saliva. Another possibility is that the patient did not eat or drink anything before inducing vomiting. If there is nothing in the stomach, emetic will not come out. Therefore, before inducing vomiting, it is recommended that the patient can drink a small amount of water or eat a little something to ensure that the vomiting can be carried out properly. However, frequent emetic is more harmful to the body. First of all, the feeling of inducing vomiting is very unpleasant. Secondly, it can cause a lot of damage to the body’s stomach and intestines, which is not conducive to the normal functioning of the stomach and intestines. To a certain extent, emetic may also cause damage to the human esophagus and vocal cords. Therefore, it is recommended that patients should not induce vomiting if it is not a special case, so as not to cause great harm to the human body.