Itch is considered by many investigators to be a form of pain. The similarity is that itch shares with pain a peripheral group of C fibers, a group of dorsal horn interneurons and a specific pathway in the anterolateral spinal cord to the brain. Both itch and pain disappear when this pathway is cut. The C fibers carry both itch and pain stimuli. However itch, can only be produced, by the superficial skin. Deeper stimuli produce pain. Another similarity is the fact that histamine placed just beneath the epidermis leads to intense itching while histamine injected deeper in the skin produces pain.^8-11

Another similarity is that a strong itch stimulus to skin such as light touch, imitates the secondary hyperalgesia in which the skin surrounding a painful focus is also painful to light touch.

The mechanism is the spreading of hyperactivity of neurons in the cord following a C fiber volley. Pain will override the itch sensation if a painful stimulus occurs in the area of the itch.^{8-11, 13}

It is likely that a healed deep burn with scar or a grafted wound has less itch because these superficial C fibers are not present nor is there a reasonable epidermal-dermal junction in scar. However, the deeper C fibers would still respond to pain and deep histamine release from the increased mast cells caused by movement, manipulation, etc. may be etiologic in the burn pain seen in these patients.

Data against itch being a form of pain is the recent finding of specific itch fibers highly sensitive to histamine. However, so far, these itch fibers do not appear to be found in all parts of the skin and the hunt goes on for itch fibers. Also, despite the fact that the nerve pathways may have common elements, the itch stimulus, likely histamine, and the pain stimulus are different.