Why does the skin become more itchy the more you scratch it?

When experiencing a skin allergy, the phenomenon of increased itching upon scratching can be attributed to the combined effects of nerve terminal sensitization, increased histamine release, and impaired skin barrier function. Upon exposure to an allergen, the immune system overreacts, releasing inflammatory mediators such as histamine, which cause local vasodilation and increased vascular permeability, leading to redness, swelling, and itching of the skin. At this point, continuous scratching stimulates the nerve endings in the skin, making them more sensitive and thereby intensifying the sensation of itching, creating a vicious cycle of "the more it itches, the more one scratches, and the more one scratches, the more it itches." Furthermore, scratching damages the skin's barrier function, allowing easier penetration of allergens and bacteria, further exacerbating the inflammatory response and causing the itching to persist and potentially spread to larger areas. Therefore, when dealing with skin allergies, it is important to avoid scratching, promptly take anti-allergic measures, and protect the skin barrier to alleviate symptoms and promote recovery.