When eye drops are put into the eyes, a small amount of eye drops will normally reach the nasal cavity through the tear dots and tear ducts, and then flow into the mouth. Because eye drops contain preservatives and many chemical ingredients, it may lead to bitter mouth and other uncomfortable symptoms. When this happens, it is recommended to rinse your mouth and brush your teeth with water immediately. After rinsing your mouth and brushing your teeth, the symptoms will be significantly reduced or even disappear completely. It is recommended to press the tear sac area for 5-10 minutes immediately after putting eye drops into the eye in the future to reduce the possibility of eye drops flowing into the nasal cavity and to avoid side effects of eye drops to the whole body.