Novel Agents for Intractable Itch

C. B. Lynde; J. N. Kraft, MD; C. W. Lynde, MD, FRCPC

Disclosures

Skin Therapy Letter. 2008;13(1):6-9. 

In This Article

Pathophysiology

The neuropathways responsible for relaying pruritus to the brain are well-known. The itch sensation is carried to the brain by a dedicated subset of nociceptive C neurons. Like the pathways for pain and temperature, the message is relayed to the spinal cord, then crosses the midline and ascends via the lateral spinothalamic tract to the thalamus, and then finally travels to the cerebral cortex.

There are many peripheral mediators of pruritus, which include histamine, cytokines (IL-2), tryptase, substance P, serotonin, and opioid peptides. The most potent from this list is histamine, which is released by dermal mast cells via many triggers (i.e., IgE crosslinking, substance P, complement C5a). This biogenic amine acts mainly as a neurotransmitter and plays a major role in skin reactions associated with urticaria, urticaria pigmentosa, and insect bites. Its role in other skin diseases (e.g., atopic dermatitis) is debatable.

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