An itch is a sensation felt on an area of skin that causes a person or animal to desire to scratch that area.
It is a distressing symptom that can cause discomfort.
Scratching may cause breaks in the skin that may result in infection.
Itching can be related to anything from dry skin to undiagnosed cancer.
The central chemical involved in itching is histamine, a molecule released by mast cells in the skin.
Histamine is the chemical that causes the itch and reddening when bitten by insects.
It binds to local nerve endings on specific receptors.
An itch from cutaneous (skin-related) stimuli, such as movement of small hairs on the body, is transmitted along the same pathway as pain.