Pain is a physiological protection mechanism to avoid harm and is also a signal of disease. However, severe pain is a malignant stimulus to the body, which will lead to a series of stress reactions in the body, causing changes in the immune and endocrine systems and complications of other diseases. Not as soon as we feel pain we need to go to the hospital to see a doctor, so what circumstances require a visit to a pain doctor? 1. Severe pain (moderate pain or more). 2.Unexplained pain. 3.Change in the nature and pattern of pain. 4. Pain relief methods are not effective. 5.Knowledge of new developments in treatment methods.