What do white lines on a nail mean?

Look at whether the line is on one nail or several, runs across or along the nail, and moves as the nail grows. A single transverse mark may appear after pressure near the nail root and gradually travel outward. Surface whiteness, roughness, splitting, thickening, or lifting suggests a different process than a smooth mark within an otherwise healthy nail. Nail fungus and nail psoriasis are possible causes of abnormal colour or texture, but neither should be diagnosed from a photograph alone.

Record when you first noticed the change and whether there was recent trauma, a manicure, new footwear pressure, or a rash elsewhere. This history can be more useful than trying to match the line to a single image online.

Protect the nail from repeated impact, keep it short, and moisturise the surrounding skin. Pause harsh nail products and avoid scraping beneath the nail. If the mark does not grow out or the nail develops texture changes, arrange an examination. [Discoloured Nails](/symptoms/nail-discoloration/) gives broader context; [Nail Fungus](/conditions/nail-fungus/) covers one possible condition.

See a clinician for pain, redness, warmth, pus, rapid change, a nail that lifts, or lines appearing on multiple nails. A persistent change should also be checked when there was no clear injury. If a nail is severely damaged after trauma, seek prompt care rather than removing it yourself.

Ask what the line’s direction and position suggest, whether the nail root or surrounding skin is involved, and whether testing would change treatment. Ask how long to observe the nail and which changes should prompt an earlier review.