What ingredient is commonly found in nail hardeners?

Nail hardeners are designed to strengthen weak or brittle nails, and one of the most commonly used ingredients in these products is formaldehyde. This compound acts as a hardening agent by promoting the cross-linking of proteins in the nails, which increases their hardness and durability. The effectiveness of formaldehyde in enhancing the structural integrity of nails makes it a popular choice in nail care products.

While other substances listed, such as alcohol and acetone, are often present in nail products, they primarily serve different purposes, such as cleaning or removing polish. Benzoyl peroxide is typically used in acne treatments due to its antibacterial properties, rather than in nail hardeners. Thus, the inclusion of formaldehyde is key to the effectiveness of nail hardeners in reinforcing nail strength.