Nail discoloration is any change from the usual color of a healthy nail, which is a pale pink plate with a white tip. Many color changes are harmless, such as staining from dark polish or a bruise after stubbing a toe. A few need medical attention. The color, the pattern and whether it grows out all help to tell them apart.
A quick guide by color
| Color | Common causes | Usually |
|---|---|---|
| Yellow | Polish staining, fungal infection, smoking, aging | Harmless if from polish; check if thick or crumbly |
| White spots | Minor knocks to the nail root | Harmless; grow out |
| White, chalky patches | Dryness after long-worn polish; some fungal infections | Improve with moisturizing; check if they persist |
| Green or green-black | Bacteria growing under a lifted nail or under artificial nails | Needs treatment advice |
| Purple, dark red or black patch | Bruise under the nail after an injury | Grows out; see a doctor if no injury or very painful |
| Brown or black stripe | Normal pigment band, a mole, or rarely melanoma | Always have a new stripe checked |
| Blue or dusky | Cold, or problems with circulation or oxygen | Seek medical advice if it persists |
| Pale or very white | Sometimes linked to anemia or other conditions | Seek medical advice |
Yellow nails
Staining from polish is the most frequent cause in people who wear dark or red shades without a base coat. The color sits on the surface and grows out. A base coat prevents it. See Base Coat vs Top Coat: Why Each Is Used.
Fungal infection makes nails yellow, white or brown, and also thick, crumbly or lifted. It usually affects toenails. See Nail Fungus: Signs and Why Diagnosis Matters.
Other causes include smoking, some medicines, psoriasis, and, rarely, conditions that affect the lungs or lymph system.
White marks
Small white spots or lines are usually the result of a minor knock to the base of the nail weeks earlier. They are not a sign of calcium deficiency, despite the common belief, and they move towards the tip as the nail grows. Whole nails that turn white, or half white and half darker, should be checked.
Green nails
A green or green-black area under the nail is often caused by bacteria that thrive in damp spaces, for example under a nail that has lifted from its bed or under an artificial nail that has come loose. Keep the nail short and dry, avoid artificial nails, and see a doctor or pharmacist for advice.
Dark patches after injury
A blow to the nail, or repeated pressure from tight shoes or running, can cause bleeding under the nail. The patch starts red or purple and turns brown or black. It moves outward as the nail grows. A large, painful bruise soon after an injury may need draining by a doctor.
Dark stripes
A brown or black line running from the cuticle to the tip is common and often harmless in people with darker skin tones, and it frequently appears on several nails. Have it checked promptly if:
- It is new, and on a single nail.
- It is getting wider or darker, or has blurred edges.
- The pigment spreads onto the skin around the nail.
- The nail is splitting or bleeding.
These can be signs of melanoma under the nail, which is uncommon but needs early treatment.
What to do first
- Remove any polish and look at the bare nail in daylight.
- Think back. Any knocks, new shoes, new polish, artificial nails or medicines?
- Photograph it and check again in two to four weeks. Stains and bruises move with growth. See Nail Ridges: What They Can Mean for ridges and other surface changes.
- Keep nails short, clean and dry.
- Do not cover a change with polish until you know what it is.
Preventing harmless discoloration
- Always wear a base coat under colored polish.
- Take polish off after a week or two, and leave nails bare for a few days. See How to Remove Nail Polish at Home.
- Wear shoes that fit, and keep toenails trimmed. See Toenail Care: Trimming and Hygiene Tips.
- Dry your feet well and change socks daily.
When to see a doctor
- Any new dark stripe or spot that you cannot explain.
- Discoloration with thickening, crumbling, lifting or pain.
- A green nail.
- Color changes on several nails at once without a clear cause.
- A change that does not grow out.
- Nail changes when you have diabetes or reduced immunity.
Related on ArniSun
- Nail Fungus: Signs and Why Diagnosis Matters
- Nail Ridges: What They Can Mean
- How to Remove Nail Polish at Home
- Toenail Care: Trimming and Hygiene Tips
- Base Coat vs Top Coat: Why Each Is Used
Sources and further reading
Frequently asked questions
Why are my nails yellow after wearing nail polish?
Pigments in dark and red polish can stain the surface of the nail, especially without a base coat. The stain is harmless and grows out.
Are white spots on nails caused by lack of calcium?
No. They are nearly always caused by small knocks to the nail and disappear as the nail grows.
When should I worry about a dark line on my nail?
See a doctor promptly if the line is new, on one nail only, widening, changing or spreading onto the surrounding skin.