Definition
Onyxis is an inflammation or infection of the nail matrix, the tissue at the base of the nail where it grows from. Think of it as a tiny zit under your nail. It can cause pain, swelling, and redness around the nail. Bacteria, fungi, or trauma can cause onyxis. In severe cases, it can lead to nail deformities or nail loss. Unlike a hangnail, onyxis involves the deeper tissues of the nail bed.