Always dry mouth in the afternoon, may be too much salt intake or too little water, but also may be due to diabetes, hyperthyroidism, psychogenic factors. 1. Physiological factors If you consume too much food with high salt content during lunch, you may experience thirst in the afternoon. Dry climate, high room temperature, etc., will lead to increased sweating, if the hydration is insufficient, thirst can also occur in the afternoon. 2. Pathological factors If in the normal diet, appropriate environment, often appear in the afternoon thirst, to consider the existence of hyperthyroidism or diabetes mellitus, caused by high metabolism, high osmotic conditions, making the amount of sweating and urination increased, resulting in excessive loss of water, thirst. Or the presence of psychological disorders, such as psychogenic thirst, can also appear thirst and drinking phenomenon. In addition to the above, there are other situations may lead to always dry mouth in the afternoon, if you can exclude physiological factors, it is recommended to go to the hospital for examination, follow the doctor’s instructions in time for targeted treatment, so as not to delay the course of the disease.