Pruritogens are substances that trigger an itch in the skin, often as part of an allergic reaction. They cause nerve endings in the skin to become sensitized, which results in an itchy sensation. Pruritogens can originate from an external or internal source. External pruritogens are substances that come in contact with the skin, such as allergens or irritants. They are found in many everyday substances, including personal care products and household chemicals. Internal pruritogens are substances that are present or produced in the body, such as histamine, serotonin, prostaglandins, cytokines, and other inflammatory molecules.
Itch is a sensation that many people experience yet don’t understand. The philosopher Aristotle (384-322 BC) recorded one of the first known descriptions of itch, characterizing how animals scratch themselves in a manner similar to modern humans.