Pruritus

Pruritus is an unpleasant sensation that provokes the desire to scratch. It can arise from skin disease, nerve dysfunction, or systemic illness.

Itch-sensing neurons: Sensory neurons that detect itch-producing signals and transmit them toward the spinal cord. These neurons carry signals that the brain experiences as pruritus.
Pruriception: The neural detection and transmission of signals that can produce the sensation of itch. Pruriception describes the sensory process underlying pruritus.
Atopic dermatitis: A chronic inflammatory skin disease characterized by itchy, relapsing eczema. It is a common skin condition in which itch is a central symptom.
Pain: An unpleasant sensory and emotional experience associated with actual or potential tissue damage. Pain and itch interact in the nervous system but prompt distinct responses.
Lichenification: Thickening and accentuation of skin markings caused by repeated rubbing or scratching. Repeated scratching in chronic pruritus can produce this visible skin change.
Histamine: A signaling molecule involved in immune responses, stomach acid regulation, and neurotransmission. Histamine released in skin can activate itch-sensing nerve endings.
Nociception: The nervous system's detection and processing of potentially tissue-damaging stimuli. Itch and pain share pathways but produce different sensations and protective behaviors.
Cholestatic pruritus: Itch associated with impaired bile formation or flow, often occurring without a primary rash. It illustrates how liver and bile disorders can cause generalized itch.
Paresthesia: An abnormal sensation, such as tingling or pins and needles, occurring spontaneously or after stimulation. Some nerve-related sensations resemble itch but do not necessarily provoke scratching.
Excoriation: A superficial skin injury caused by scratching or other mechanical trauma. Scratching itchy skin can break the barrier and increase risk of infection.

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