system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does scratching an itch make it stop itching?
gpt
The itch is usually caused by histamine, a substance that exists in basophiles, which are a type of white cell that moves to inflammated parts of the body (for example, a mosquito bite). Due to the inflammation the basophiles release the substance and when you scratch it you make them release it all the more fast and effectively - that is why at first you feel itchier when you scratch. Eventually all the basophiles in that spot have no more histamine to release and the itch stops.