What causes an itch?!


Question: I've always wondered this.


Answers: I've always wondered this.

Itch originating in the skin is considered pruritoceptive and can be induced by a variety of stimuli, including mechanical, chemical, thermal, and electrical stimulation. The primary afferent neurons responsible for histamine induced itch are unmyelinated C-fibers. In human C-fiber nociceptors, two major classes exist: mechano-responsive nociceptors and mechano-insensitive nociceptors. Mechano-responsive nociceptors have been in shown in studies to respond to mostly pain and mechano-insensitive receptors respond mostly to itch induced by histamine. However it does not explain mechanically induced itch or when itch is produced without a flare reaction which involves no histamine. Therefore it is possible that pruritoceptive nerve fibers have different classes of fibers, which is currently unclear in current research.[1]

Studies have been done to show that itch receptors are only found on the top two skin layers, the epidermis and the epidermal/dermal transition layers. Shelley and Arthur had verified the depth by injecting individual itch powder spicules (Mucuna pruriens) and found that maximal sensitivity was found at the basal cell layer or the innermost layer of the epidermis. Surgical removal of those skin layers removed the ability for a patient to perceive itch. Itch is never felt in muscle, joints, or inner organs, which show that deep tissue does not contain itch signaling apparatuses.



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