Menthol has a cooling effect on skin and is a counter-irritant—a substance that distracts from the itch. It is an organic compound sourced from peppermint and other mint plants. It can also be made synthetically.
Some OTC products like Gold Bond Medicated Anti-Itch Lotion contain menthol. You can also find menthol in peppermint essential oil. However, you must always dilute essential oils with a carrier oil so they are safe for use on irritated skin.