Lateral Nail Folds: Anatomy, Function, and Salon Relevance

The lateral nail folds — also called the nail walls or side walls — are the two longitudinal ridges of skin running along the medial (inner-facing) and lateral (outer-facing) edges of the nail plate. Lateral means pertaining to the side, and these folds run from the base of the nail — where they meet the proximal nail fold — down to the free edge, where they meet the skin of the fingertip.

Contributing to the c-curve

The lateral nail folds also influence the transverse arch — the c-curve — of the nail plate. The way the lateral folds border the nail plate on each side, combined with the curvature of the underlying nail bed, contributes to the natural arch of the plate across its width. Nails with very prominent lateral folds tend to have a more pronounced c-curve. Nails with lower or less defined lateral folds tend to be flatter across the plate.

Product flooding at the lateral folds

Product that flows onto the lateral nail fold skin during gel or enhancement application and remains in contact while uncured is one of the pathways to contact sensitisation. Keeping product off all skin — including the lateral folds — throughout the service is both a quality and a safety standard.

Ingrown nail — onychocryptosis

When the edge of the nail plate grows into the lateral nail fold rather than along the lateral groove, the fold becomes inflamed, painful, and sometimes infected. This is one of the most common conditions affecting the lateral nail folds and is a contraindication to nail services in the acute phase. See: Ingrown Toenail →

Paronychia

Infection can occur at either lateral nail fold — typically presenting as redness, swelling, and tenderness along the side of the nail. As with proximal fold paronychia, acute infection is a contraindication to nail services in that area.

Callus and thickened skin

Thickened, hard skin at the lateral nail folds — particularly in clients who work with their hands or whose nails press frequently against adjacent fingers — is a common finding. This is manageable through gentle e-file work with appropriate bits in a professional nail service.

What are the lateral nail folds?

The lateral nail folds are the two ridges of skin running along the left and right sides of the nail plate from the base of the nail to the free edge. They border the nail plate on each side, house the lateral grooves through which the nail plate edges grow, and form part of the three-sided skin frame surrounding the nail.

What is the difference between the lateral nail fold and the lateral nail groove?

The lateral nail fold is the raised ridge of skin running along the side of the nail. The lateral nail groove is the narrow channel between the inner surface of that fold and the edge of the nail plate — the track through which the nail plate edge grows. The fold is the structure; the groove is the space between the fold and the plate.

Why do lateral nail folds matter when choosing a dual form?

The dual form must cover the growth points — where the nail plate meets the lateral folds — without compressing the folds or leaving gaps. A form that is too narrow compresses the lateral folds and causes pressure, uneven product distribution, and side lifting. Correct form selection accounts for the width and curvature of the nail at the lateral folds, not just the overall width of the nail plate.

Can the lateral nail folds affect the c-curve?

Yes — the prominence of the lateral nail folds contributes to the transverse arch of the nail plate. Nails with more prominent lateral folds tend to have a deeper natural c-curve. Nails with lower, less defined folds tend to be flatter. This is one of the reasons c-curve depth varies between clients and must be assessed individually before enhancement services.