Hyperalgesia

Hyperalgesia refers to a heightened sense of sensitivity to pain that might be caused by damaged nociceptors (see nocicpetion) or nerves in the peripheral nervous system. This hypersensitivity can be a temporary reaction to illness as part of an evolved response to infection.

For instance, when a person has the flu it is very common to have body aches which seem as if pain is occurring all over. Opiod-induced hyperalgesia is when individuals who use opiods (morphine, codeine, heroin, etc) experience nociceptor sensitivity and become hypersensitive to painful stimuli.