Are your nail sinuses always dirty after prep? Here’s why.

What Are the Nail “Sinuses,” Exactly?

In salon language, the nail sinuses are the small corner recesses at the base of the nail plate, tucked under the proximal nail fold and along the start of the lateral nail folds. Think of them as tiny pockets at the left and right “corners” of the cuticle area where dust and dead skin love to hide. These corners are not the matrix itself. The matrix is the living tissue under the proximal fold that produces the nail plate, while the sinuses are just the entry recesses where the plate slides under the fold and side walls.

Why they get “dirty”: during prep, micro-dust from filing and loosened cuticle (true cuticle and eponychium remnants) accumulate in those recesses. If you don’t lift the proximal fold enough, keep the wrong bit angle, or work with too little stretch, you’ll leave debris behind — exactly the issues listed below.

If you're still seeing dust and stuck skin after cleaning the sinuses, chances are your technique needs a tune-up.

How to locate them on a client:

• Ask the client to relax the finger.

• Gently lift the proximal nail fold with a pusher to reveal the corners.

• Slightly stretch the side walls to “open” the lateral nail folds. You’ll see the little pocket at each corner — that’s the sinus area you need to clean.

Here's what to watch out for:

1. You didn’t open the proximal fold properly.

Always lift the cuticle gently with a pusher before using scissors.
→ No lift = no access for your tools.

2. Your bit angle is wrong.

Use a 2.1–2.3 mm red flame bit, and work at a 30° angle.
→ Only the side should touch the skin — not the tip, not the belly!

3. You’re pressing too hard with the bit.

Stretch the client’s skin and work from the center outward at a diagonal.
→ If the skin folds over, you won’t clean the area properly.

4. Your e-file is too weak or too slow.

Work at 15,000–20,000 RPM. Weak machines force you to push harder and risk damage.

Precision in the sinus area starts with using the right tools. A professional e-file nail drill paired with high-quality nail drill bits allows you to work efficiently and safely, reaching tight corners without leaving debris or causing discomfort to the client.

Common mix-ups to avoid:

• Sinuses ≠ Matrix. Matrix makes the nail; sinuses are just the corner recesses where the plate passes under the fold/side walls.

• Cuticle vs. Eponychium vs. Fold. The cuticle is the non-living tissue on the plate. The eponychium is living skin that produces the cuticle. The proximal nail fold is the skin “hood” protecting the matrix. Keeping these straight helps you remove only what you should.

Red flags (refer out): inflamed, painful, or swollen corners (paronychia) need a pause and possibly medical care — don’t “chase” debris in infected tissue.