The primary afferent neurons responsible for histamine-induced itch are unmyelinated C-fibres.Two major classes of human C-fibre nociceptors exist: mechano-responsive nociceptors and mechano-insensitive nociceptors. Mechano-responsive nociceptors have been 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 itch produced without a flare reaction that involves no histamine. Therefore, it is possible that pruritoceptive nerve fibres have different classes of fibres, which is unclear in current research.Studies have been done to show that itch receptors are found only on the top two skin layers, the epidermis and the epidermal/dermal transition layers. Shelley and Arthur verified the depth by injecting individual itch powder (Mucuna pruriens) spicules and noting that maximal sensitivity occurred 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 or joints, which strongly suggests that deep tissue probably does not contain itch signaling apparatuses.Itch is often classified as that which is histamine mediated (histaminergic) and nonhistaminergic. Sensitivity to pruritic stimuli is evenly distributed across the skin and has a clear spot distribution with similar density to that of pain.
Accidental may refer to:

Accidental (music), a symbol which changes the pitch of a note
Accidental (album), by Fred Frith
Accidental (biology), a biological phenomenon more commonly known as vagrancy
The Accidental, a 2005 novel by Ali Smith
The Accidental (band), a UK folk band
Accidental property, a philosophical term

See also
Accidence (or inflection), a modification of a word to express different grammatical categories
Accident (disambiguation)
Adventitious, which is closely related to "accidental" as used in philosophy and in biology
Random, which often is used incorrectly where accidental or adventitious would be appropriate