Caustic alkalis, also known as lyes, are highly corrosive substances that can cause severe burns and tissue damage. They are typically composed of sodium hydroxide or potassium hydroxide, and are used in a variety of industrial and household applications. Lyes are often used to make soaps, detergents, and other cleaning products, as well as for food processing and manufacturing. In addition, they are used in the production of paper, textiles, and other materials.