Referred Itch - Pathophysiology

Pathophysiology

An itch, also known as pruritus, is classified as a sensory stimulation to scratch a certain area of the skin. An itch can be a fleeting sensation, as with a random tickle or prick, or persistent, as with a rash such as eczema or other skin irritant such as an allergen. Itch has been demonstrated to be closely related to pain and to share many of its physiological mechanisms. The relationship between pain and itch is evident in the fact that itch sensations occur along a similar neurological and sensory pathway as sensations of pain, and the fact that individuals who are insensitive to pain are also insensitive to itch.

Itch is induced by mechanical, chemical, thermal, or electrical stimuli of sensory receptors in the peripheral nervous system, or by psychological prompts. The receptors that are responsible for the sensation of itch caused by environmental stimuli are found within the upper layers of the skin. Once stimulated, usually by histamine within the body, a signal is sent though the peripheral nervous system to the brain (thalamus), where the information is processed and the command for the bodily response is issued. Itch can also originate as a result of damage to the nervous system (central or peripheral) or in response to the presence of excess opioids.