What is the Difference Between Allodynia and Hyperalgesia?

Allodynia and hyperalgesia are both pain-related conditions that can occur in patients with neuropathic pain. The main differences between them are:

• Definition: Allodynia is pain due to a stimulus that does not normally elicit pain, while hyperalgesia is increased pain from a stimulus that normally provokes pain.
• Sensitivity: Allodynia involves pain from a stimulus that wouldn't normally provoke pain, and it is defined by pain from a stimulus that should only cause sensation. Hyperalgesia, on the other hand, is a condition that causes extreme sensitivity to pain, making the pain more intense than it should be.
• Responses: With allodynia, the response to the stimulus differs from those who have normal sensation, while in hyperalgesia, the response to the stimulus is the same as those who have normal sensation, but it is an exaggerated response.
• Clinical Manifestations: Allodynia and hyperalgesia are clinical terms that do not imply a mechanism, and their clinical presentation differs between different pain conditions. Allodynia can be further classified according to the sensory modality (touch, pressure, pinprick, cold, and heat) that is used to elicit the sensation.

In summary, allodynia involves pain from a stimulus that doesn't usually cause pain, while hyperalgesia is increased pain from a stimulus that does normally cause pain. Both conditions can co-exist and can be present in various peripheral neuropathies and central pain disorders.

Comparative Table: Allodynia vs Hyperalgesia

Allodynia and hyperalgesia are two distinct pain conditions that can occur in various peripheral neuropathies and central pain disorders. Here is a table highlighting the differences between the two:

Both conditions can be seen in patients with neuropathic pain, and better understanding of their mechanisms might provide clues to the underlying causes and improve treatment strategies.