What ingredient is commonly found in nail hardeners?

Formaldehyde is commonly used in nail hardeners due to its chemical properties that help strengthen nails. It acts as a bonding agent that can effectively enhance the structure of weak or brittle nails, making them harder and less prone to breaking. The effectiveness of formaldehyde hinges on its ability to create cross-links between the keratin proteins in the nails, which increases durability and resilience.

In contrast, while acetone is a solvent typically found in nail polish removers, it does not contribute to hardening nails. Alcohol may be included in some nail products, but its primary role is usually related to sanitization or as a drying agent, not hardening. Vitamin E, although beneficial for skin and nail health, primarily serves as a moisturizer and antioxidant rather than a nail hardener. Therefore, formaldehyde is specifically recognized for its role in enhancing the hardness of nails in formulations designed for that purpose.