Three Nails, Three Different Answers

Growth math: fingernails grow roughly 0.1 mm per day, about 3 mm per month, with full replacement from matrix to free edge taking 4–6 months. Ten weeks is about 70 days, so the point on the plate that was at the matrix during the illness has traveled roughly 7 mm toward the free edge.

That matches exactly what you see: a groove 7 mm from the cuticle means the matrix was interrupted about ten weeks ago. A high fever or severe illness temporarily halts cell division in the matrix, producing a transverse depression - Beau's lines - on every nail in production at that moment. The fact that all ten are affected, the timing is symmetric, and the client reports no pain fits the history.

Service decision: this is a resolved systemic event, not an infection. The grooves are cosmetic and growing out and the skin is intact. Service is appropriate, with two adjustments: use a gentle hand file rather than a coarse one at the groove, and tell her the ridges will disappear on their own over the next few months so she doesn't expect a product to "fix" them. If she had described an active illness, a new medication, or the grooves continued to appear, that would change the answer.

Do not polish over it and do not accept the request as stated. The features that matter:

• A single band (not multiple symmetric streaks), which points to a localized process rather than a pigmentation pattern.
• Widening over eight months - a benign nevus is typically stable; progressive widening suggests activity.
• Pigment on the surrounding cuticle tissue (Hutchinson's sign) - pigment that has crossed from the nail plate into the skin is the classic warning for subungual melanoma.
• An incomplete prior evaluation with no follow-up.

Melanoma of the nail unit is often diagnosed late precisely because it is covered with polish and treated as a cosmetic problem. Covering it removes the only thing a clinician can watch, and it delays the diagnosis that determines outcome.

What you do: decline the color on that nail, explain in plain language that a changing pigmented band is something a dermatologist needs to see and that you are not qualified to diagnose it, and urge an appointment - soon, not eventually. Document the referral and the appearance in your notes, offer to polish the other nine, and offer a clear or strengthening service only if she insists and only after you have explained the risk.

Do not apply a gel overlay over that toenail and do not put the foot through a full pedicure service on that nail. Thickened, crumbly, yellow-brown nail with subungual debris is consistent with a fungal infection (onychomycosis), and possibly with a co-existing bacterial problem under the free edge. A gel overlay seals moisture and organism against the plate, may worsen the condition, and creates a reservoir you cannot clean. She needs a podiatrist or physician; a salon cannot diagnose or treat this.

If you do anything at all: clean and file only the unaffected nails, do not file the crumbly nail (a file used on it becomes contaminated porous waste), discard the file and any debris-laden disposable, and disinfect the basin and your metal tools exactly as for any other client - an infected client does not get a "better" protocol, every client gets the full one.

Follow-up: tell her not to share clippers or shoes, that the other foot was likely the same problem, and that the overlay should wait until a clinician confirms the nail is clear. Document the presentation and the referral in her record so the next technician sees the same note.