“Pruritus [itching] is caused by a complex process, involving different neurotransmitters, the hormonal system, blood vessels of the skin, psyche, and other systems. Some aspects of this process seem to be influenced by THC and might explain positive effects reported by a number of patients. The immunodulatory action of THC suggests an antiallergic effect.”

--Grotenhermen, Russo. Cannabis and Cannabinoids: Pharmacology, Toxicology, and Therapeutic Potential. New York: The Hawthorn Integrative Healing Press, 2002  Grotenhermen, “Review of Therapeutic Effects.” Chapter 11, p. 130