Lye/laɪ/ Definition 1 of 2Pro Tip 1/3Safety First Lye can cause chemical burns. Handle with care and protection. Always use gloves when handling lye to avoid skin irritation. Pro Tip 2/3Industrial Strength Lye is used in heavy-duty cleaning, its strength is notable. Industrial cleaners contain lye for its powerful cleaning properties. Pro Tip 3/3Soap Making Lye is a key ingredient in traditional and homemade soap recipes. She mixed lye with oils to start the soap-making process.