STOP ALL FLUID INSULATIONS 4 HOURS BEFORE YOUR CHECK IN TIME. You can relieve dry mouth by chewing gum or sucking on mints. It is OK to clean your teeth and use mouthwash on a regular basis. Wear loose-fitting clothing and warm socks. If you have a cold or the flu, do not go to the hospital. Stay home. Endoscopic procedures usually are not painful but sometimes patients may feel mild discomfort during the procedure. Pain medication can be given before the test if needed. Mouthwashes contain alcohol which is used for its antiseptic properties. However, alcohol can cause drying out of the mucous membranes in the nose and throat leading to pain when swallowing or talking. This is why doctors usually advise against using mouthwashes before an endoscopy.