Undecylenic Acid USP
The first ingredient on the label and the only one with a printed amount: 5%. It is an eleven-carbon unsaturated fatty acid, produced industrially by cracking ricinoleic acid out of castor oil — which is why the vendor's own photograph for it is castor beans rather than anything nail-related. Undecylenic acid is a long-standing ingredient in nail-care products. KlaroNail carries no Drug Facts panel and is sold as a cosmetic, so this page reports the printed 5% and stops there.