What ingredient is commonly used in nail hardeners?

• A. Keratin
• B. Formaldehyde
• C. Sulfur
• D. Acetone

Answer: (B)

Formaldehyde is commonly used in nail hardeners due to its ability to create cross-links between the keratin proteins in the nails. This process strengthens the nail structure, making it less prone to breakage and peeling. Nail hardeners containing formaldehyde work by chemically bonding with the natural nail plate, enhancing its durability.

While keratin is a protein found naturally in nails, it is not an additive in nail hardeners; rather, it is a component of nails themselves. Sulfur is also not used for this purpose, as it does not contribute to nail hardening in cosmetic formulations. Acetone, commonly known as a nail polish remover, does not have hardening properties and can actually weaken nails with excessive use. Thus, the key function of formaldehyde in nail hardeners makes it the correct choice.