Development of itching
Itching (pruritus) occurs when the free nerve endings of the skin are irritated by messenger substances from the skin and blood - for example histamine. An insect bite can also trigger pruritus, as can serious diseases. The nerves of the spinal cord transmit the feeling of pruritus to the brain. There, the desire for scratching is triggered.
Pruritus triggers scratching or rubbing of the skin. Strong scratching causes pain and reduces the perception of pruritus for a short time. Long-term further scratching is stimulated in this way. Persistent or severe scratching damages the skin. This maintains or even intensifies inflammatory processes, which in turn promotes pruritus. A vicious itch-scratch cycle develops from pruritus and mechanical stimulus response. This often leads to the habit of a daily ritual with automatic and partly unconscious scratching behaviour.