In accordance with current views on pain, a distinction is made, on a physiological basis, among ´normal´, or nociceptive pain, inflammatory pain and neuropathic pain. ´Normal´, nociceptive pain is a reaction to possible or actual tissue damage. Inflammatory pain is a response to actual tissue damage, in which not only nociception occurs but the sensitivity of nocisensors changes through morphological transformation. This phenomenon is called sensitization and lies at the root of multiple types of chronic pain. Sensitization also plays an important role in neuropathic pain as a result of damage to the neuronal structures themselves.