Introduction to Hyperalgesia
Hyperalgesia is a medical condition that causes an increased sensitivity to pain. Individuals with hyperalgesia experience pain when exposed to normal stimuli. They also experience worse pain, when exposed to painful stimuli, than someone who does not have the condition. Hyperalgesia is caused either by injury or opioid use.
Hyperalgesia is divided into two categories: primary and secondary. Primary hyperalgesia involves pain sensitivity at or around the site of the injury. Secondary hyperalgesia occurs when the pain spreads to other areas of the body. Opioid-induced hyperalgesia is a specific type of hyperalgesia that can occur as a result of taking opioid medications.
The chief symptom of hyperalgesia is increased pain sensitivity (without new injury, damage to an existing injury, or worsening of a medical condition).
Hyperalgesia develops when immune-system cells interact with the peripheral nervous system, releasing pain-producing chemicals. The condition is thought to be the result of an allergy or inflammatory response. The pain-producing chemicals enhance the responsiveness of the nerve receptors, leading to increased pain.
Medical conditions that may cause hyperalgesia include, but are not limited to, the following:
- Complex regional pain syndrome
- Postherptic neuralgia