Nail strengthener (sometimes called nail hardener) is a clear base coat polish painted onto the nails to help nourish and strengthen fingernails and toenails. Each brand of nail strengthener has its own formula, but most nail strengtheners contain a mix of vitamins, herbs, proteins, oils and calcium made to fortify the nails and lead to less cracking, splitting and breaking.
Popular brands of nail strengthener include O.P.I. Nail Envy Nail Strengthener, 100 Percent Pure horsetail Base Coat Polish, Formula X Strengthen Nail Strengthener, butter London Horse Power Nail Strengthener, Essie Grow Stronger, Revitanail, Sally Hansen Hard As Nails, and Orly Nailtrition.