The tooth hurts when it encounters cold water.1. It may be because the tooth enamel has been worn down during long-term use and will become very sensitive after encountering such stimuli as hot, cold, sour or sweet, producing painful sensations. If this situation is not very serious, try to avoid stimulation, you can use commercially available anti-allergy toothpaste can. If the allergy is serious and has affected the patient’s normal life and eating, you can go to the dental clinic for desensitization treatment. 2. The pain when encountering cold water may be due to dental caries, which has developed to a certain degree and has damaged the dental pulp, and the dental pulp has produced certain lesions. At this time, when encountering cold water or hot water, the nerve of the tooth will produce painful feeling. If the tooth decay is not treated in time, this secondary pain will soon turn into an autonomous pain.