Itching is the result of damage to cells in our skin. As a result of the damage, substances like histamine ( the amine that causes widening of blood vessels and plays a role in allergic phenomena) are set free and irritate the nerve fibres in the skin. These send signals, similar to pain signals, to the central nervous system.
One can compare the nerve fibres to telephone lines and the central nervous system to a switchboard. The switchboard routes incoming telephone calls, and makes sure that only one line at a time is connected with each telephone number. By occupying the line you can prevent others from having a conversation with the same number. Likewise, the itch message can be blocked by occupying the central nervous system with another signal, for example, the one generated by scratching, which is less irritating.
One can compare the nerve fibres to telephone lines and the central nervous system to a switchboard. The switchboard routes incoming telephone calls, and makes sure that only one line at a time is connected with each telephone number. By occupying the line you can prevent others from having a conversation with the same number. Likewise, the itch message can be blocked by occupying the central nervous system with another signal, for example, the one generated by scratching, which is less irritating.
