Final answer:
Nerve growth factor (NGF) is a protein involved in the development and survival of nerve cells. It is a chemical mediator that contributes to the sensation of itching in the skin.
Step-by-step explanation:
Nerve growth factor (NGF) is a protein that plays a crucial role in the development and survival of certain types of nerve cells. It is involved in the growth, maintenance, and repair of the nervous system. NGF is produced by various cells in the body, including immune cells, and its levels can increase in response to injury or inflammation. In the context of cutaneous itch, NGF has been identified as one of the chemical mediators that contribute to the sensation of itching in the skin.