Because taro skin contains very alkaline mucus, called grass acid base, which has a strong stimulating effect on the skin. Saponin in taro skin makes hands itch very much. The preventive method is to wash hands with vinegar before peeling taro. The acidity of vinegar can neutralize this alkali. If you already feel itchy, you can wash it with warm water or bake it on the fire for a while, and the itchy feeling will disappear. You can also wipe your hands with peels such as lemons and oranges.