What is pain? Pain is a sensation triggered by the nervous system in response to tissue damage or other damage to the body. Pain can be a dull, achy, stabbing, shooting, burning, or a pins-and-needles sensation. You may feel pain in a specific area of the body, such as your back, or you may feel aches and pains all over, such as when you have the flu (influenza). The experience of pain is invariably tied to emotional, psychological, and cognitive factors. Pain can be due to a wide variety of diseases, disorders and conditions that range from a mild injury to a debilitating disease. Pain can be categorized as acute, chronic, referred, cancer, neuropathic, and visceral. Acute pain is experienced rapidly in response to disease or injury. Acute pain serves to alert the body that something is wrong and that action should be taken, such as pulling your arm away from a flame. Acute pain often resolves within a short time once the underlying condition is treated. Chronic pain is defined as lasting more than three months. Chronic pain often begins as acute pain that lingers beyond the natural course of healing or after steps have been taken to address the cause of pain. Referred pain is pain that originates in one part of the body but is felt in another part of the body. Cancer pain is due to malignancy. Neuropathic pain is caused by damage to the nervous system and is often perceived as tingling, burning, and pins-and-needles sensations called paresthesias. Visceral pain is caused by a problem with the internal organs, such as the liver, gallbladder, kidney, heart or lungs. Recent studies have found that some people with chronic pain may have low levels of endorphins in their spinal fluid. Endorphins are neurochemicals, similar to opiate drugs (like morphine), that are produced in the brain and released into the body in response to pain. Endorphins act as natural pain killers. Chronic pain most often affects older adults, but it can occur at any age. Chronic pain can persist for several months to years. Pain can be a sign of a serious disease or condition. If you are experiencing severe pain, chest pain, difficulty breathing, bleeding symptoms, or a change in consciousness, seek immediate medical care (call 911). If your pain is persistent, or causes you concern, talk with your medical professional about your symptoms. Research into the diagnosis and treatment of chronic pain is ongoing, so ask your health care professional for the latest information.