Because taro scalp contains highly alkaline mucus, called oxalic acid alkali, which has a strong irritating effect on the skin. The saponin in the taro scalp makes the hands very itchy. The preventive method is to wash hands with vinegar before peeling the taro. The acidity of vinegar can neutralize the alkali. If you already feel itchy, you can wash it with warm water or heat it over a fire for a while, and the itching feeling will disappear. You can also use lemon, citrus, etc. peel to rub your hands.