Toenail Discoloration: What Each Color Means
Yellow, white, brown, green, red or grey: the usual cause behind each color, what you can safely watch at home, and which changes should be checked.
Toenail discoloration is any change from the normal see-through look of a toenail, and the color itself is one of the best clues to the cause. The color can sit on the surface of the nail, inside it, or in the skin underneath, and where it sits matters as much as the shade.
Below: a one-table summary, then each color in turn.
ASG Foot & Ankle patient education. Updated October 23, 2026. General information, not a diagnosis.
The short answer
Toenail discoloration is most often a fungal infection, which usually turns the nail yellow, white or brown, starts at the tip and thickens the nail. But fungi cause only about half of abnormal-looking nails. The rest are mostly polish staining (yellow or red, fading about two weeks after the polish comes off), blood under the nail (red or purple, darkening to brown or black), Pseudomonas bacteria (green) or a pigment stripe (brown or black). Most are not urgent, but a stripe that is new, widening or spreading onto the skin, a painful nail with pus, or any nail change with diabetes or poor circulation should be checked promptly.
Get It Seen Promptly If
- •A brown or black stripe is new, widening, darkening, wider than about 3 mm, or on a single nail with no injury to explain it
- •Dark pigment is spreading onto the cuticle or the skin around the nail
- •The nail is lifting and the toe is painful, red, swollen or leaking pus
- •You have thin red lines under several nails along with a fever or feeling unwell
- •The toe itself, not just the nail, is turning blue, grey or black, or is cold and numb. That is same-day care
- •You have diabetes, neuropathy, poor circulation or a weakened immune system. Have any nail change checked rather than watched
Toenail Discoloration by Color: The Quick Guide
Find your color, then read its section below. The urgency column assumes you do not have diabetes or circulation problems; if you do, move every row up a level.
| Color | Most common causes | What to do | How urgent |
|---|---|---|---|
| Yellow | Fungus; staining from dark polish; rarely yellow nail syndrome or a medicine | Go polish-free and watch; get a thick or crumbly nail tested | Routine |
| White | Spots from minor knocks; white surface fungus; chalky patches after polish removal | Let spots grow out; test chalky, spreading patches | Routine |
| Brown | Fungus; old blood; staining; a pigment stripe | Photograph and watch; have any stripe checked once | Promptlyfor a new or changing stripe |
| Black | Blood under the nail; dark fungal debris; rarely melanoma | See the black toenail guide below | Promptlyunless it is clearly a bruise growing out |
| Green | Pseudomonas bacteria under a lifted nail | Keep it dry and book an appointment for treatment | Promptly |
| Red or purple | Fresh blood from an injury or shoe pressure; thin splinter lines | Ice and protect it; get seen for severe or worsening pain | Routinesame day after a crush injury with severe pain |
| Blue or dusky | Poor circulation | A toe that stays blue, cold or painful needs same-day care | Urgent |
| Grey | Some medicines; silver exposure | Bring your medication list to an appointment | Routine |
Yellow Toenails
A yellow toenail is most often a fungal infection (onychomycosis). Nail fungus affects up to 13.8% of adults in North America, and age over 60, diabetes, poor circulation and repeated nail injury all raise the risk. A fungal nail typically yellows from the tip or a side edge first, then spreads back toward the cuticle, becoming thicker and crumbly, with debris packed underneath.
Toenail Discoloration From Nail Polish
Pigmented polish, especially when it stays on for a week or more, can stain the keratin of the nail, most often yellow or red. A dermatology review describes this as a harmless stain that resolves in about two weeks once the polish is off, and notes that a base coat does not always prevent it.
- •Staining looks like: an even tint across the nails you paint, on a nail that is otherwise smooth, thin and attached.
- •Test it: leave the nails bare for a few weeks and photograph them. A stain fades; fungus does not.
- •Not staining: a nail that is thick, crumbly or lifting, or color that is still spreading after weeks without polish.
For a fuller side-by-side of staining, bruising and fungus, see is it just discoloration, or a fungal nail?
Yellow nail syndrome (rare)
Very occasionally, many or all nails turn yellow or greenish, thicken, curve more than usual and grow at roughly half their normal speed. This is yellow nail syndrome, estimated at fewer than 1 in a million people, usually after age 50. The nails come with leg swelling (lymphedema), a lung problem such as a chronic cough or fluid around the lungs, or both, so it needs a doctor, not just nail care.
Some medicines also tint nails yellow, including tetracycline antibiotics. Medicine-related changes tend to show up on several nails at once, fingernails included, rather than on one toe.
White Toenails and White Spots
White spots from minor knocks
Small white spots or lines (leukonychia) are usually harmless, most often from bumping the nail, tight shoes or forceful nail care. The popular idea that they mean a calcium or zinc deficiency is unproven. They grow out with the nail, which takes 12 to 18 months for a toenail.
White superficial fungus
A form of fungus that lives on the surface, making chalky white patches or a whole white nail that feels soft, dry and powdery. Scraping it can spread it, so wash your hands after touching it.
Chalky patches after polish
Called keratin granulations: white streaks, spots and patches where polish bonded to the nail and pulled away its top layers on removal. It is surface damage, not infection, but it looks very like white superficial fungus.
Telling them apart: chalky patches that appeared right after removing polish point to keratin granulations. Chalky patches that keep spreading, or appear on nails you never paint, should be tested for fungus.
Brown Toenail Discoloration: Fungus, Staining or a Streak
Brown toenail discoloration usually comes from one of four things, and the shape of the brown is the best clue:
Fungus
Often brown in darker skin tones and yellowish brown in lighter ones. Patchy, starting at the tip or a side edge, in a thick, crumbly nail.
Old blood
Blood under the nail starts red or purple and turns dark brown or black. It has a clear edge and moves toward the tip as the nail grows.
Staining
Hair dye, henna, nail enamel and paint can tint the nail from the outside, on a nail of normal thickness.
A pigment stripe (melanonychia)
A brown or black band from the cuticle to the tip, made by pigment cells at the nail root. Shoe friction, a toe deformity, pregnancy and some medicines can trigger one.
Dark brown toenails on several toes are most likely fungus, staining or normal pigment. Brown stripes are very common in darker skin, found in more than 77% of Black adults over 20 in one older review. A single new stripe is the one to have checked.
When a brown or black stripe needs checking
Most stripes are benign, but rarely a stripe is the first sign of melanoma under the nail. It is most common on the thumb and the big toe, more common in older adults and people with skin of color, and is often diagnosed at a later stage than melanoma on the skin. Have a stripe examined promptly if you notice:
- •A new stripe in an adult, especially in lighter skin
- •A stripe that is changing: getting wider or darker
- •A band wider than about 3 mm, or one that is wide and irregular
- •Only one nail affected, especially the big toe, with no injury to explain it
- •Pigment spreading onto the cuticle or the skin around the nail (the Hutchinson sign)
- •The nail splitting or lifting along the band, or a bump under the nail
If a stripe looks suspicious, a biopsy is the only way to be certain. The full checklist and a simple photo test are in black spot under toenail.
Black Toenails
Black is usually the darkest stage of the causes above: dried blood under the nail from an injury or from toes hitting the front of a shoe, or dark fungal debris. We cover it fully in why toenails turn black. If the toe itself, not just the nail, is turning black, blue or grey, that is a circulation problem until proven otherwise; read toe turning black and get seen today.
Green Toenails: Green Nail Syndrome
A green, green-yellow, green-brown or green-black toenail is usually an infection with Pseudomonas bacteria, called green nail syndrome or chloronychia. The bacteria make blue-green pigments that stain the nail.
Why it happens
- The bacteria settle in the damp gap under a nail that has lifted off its bed
- A chronically inflamed skin fold at the nail base, frequent soaking and repeated knocks all raise the risk
- It often sits on top of fungus or psoriasis, the conditions that lift the nail in the first place
What treatment involves
- Trimming away the lifted part of the nail and keeping the foot dry
- A lab sample to check for fungus at the same time
- An antiseptic or antibiotic solution, often for 1 to 4 months, or antibiotic tablets for about 2 to 3 weeks instead
It is often painless and not an emergency, but it needs treating, sooner if you have diabetes. Spreading redness, swelling, warmth or pus is a more urgent situation.
Red, Purple or Blue Under the Toenail
Red or purple: blood under the nail
A subungual hematoma, a bruise under the nail, starts red or purple and gradually turns dark brown or black. One from a crush injury can throb badly, and draining it relieves the pressure. Get seen for intense or worsening pain, a deep cut, or a toe that may be broken. Otherwise it grows out over many months. Bruised toe healing time covers the toe itself.
Thin red or brown lines: splinter hemorrhages
Tiny lengthwise lines that look like splinters under the nail. Trauma, psoriasis and fungal infection are common causes, and they appear in up to 20% of people without any heart infection. They are a classic sign of a heart valve infection, though they show up in only about 15% of people who have one. Lines under several nails together with a fever or feeling unwell should be checked the same day.
Blue or dusky: circulation
A blue or dusky toe under the nail points to circulation. Narrowed leg arteries can turn the skin paler than usual or blue and leave toenails brittle and slow-growing. A toe that stays blue, cold, numb or painful, or changes color quickly, needs same-day care. More in poor circulation warning signs.
Grey Toenails
Two causes of grey or blue-grey nails are easy to miss. The antibiotic minocycline can leave a bluish grey tint in the nail bed that, unlike a bruise, does not move forward as the nail grows, and long-term silver exposure turns nails blue-grey. Both tend to affect several nails, so bring your medication and supplement list to an appointment.
Grey or dusky skin around the nail is a circulation sign instead; see the blue section above.
What Color Is Toenail Fungus?
Most often yellow, brown or white. Dermatologists also see orange, greenish black and black. Color change is often the first sign, and it usually begins at the tip of the nail and spreads toward the cuticle. In darker skin tones a thickened fungal nail often looks brown; in lighter skin, yellowish brown. The pattern matters as much as the color:
| Pattern | What it looks like | Worth knowing |
|---|---|---|
| Distal lateral subungual (most common) | Yellow, brown or white change starting at the tip or a side edge, with lifting, thickening and debris underneath | Most often the big toe and the little toe |
| White superficial | Chalky white, occasionally black, patches on the surface of the nail | The nail feels soft, dry and powdery; scraping it can spread it |
| Proximal subungual | White change starting at the cuticle end and spreading forward | Can signal a weakened immune system, so it deserves a medical check |
| Total dystrophic | The whole nail thick, crumbling and yellowish | Usually long-standing infection |
Nail fungus is usually painless, though a thick nail can hurt in shoes or when walking.
Treatment options are on our toenail fungus page; see also OTC toenail fungus treatments compared and laser toenail fungus treatment recovery.
Discolored Toenails That Are Not Fungus
Fungi cause only about 50% of abnormal-looking nails. The other half is everything else on this page, plus nail psoriasis, which affects the nails of 50% to 90% of people with psoriasis. These clues point away from fungus:
- Only one nail changed, after a stub, a dropped object or a long run in tight shoes
- The color sits on the surface and the nail is smooth, thin and attached
- A mark with a clear edge that moves toward the tip as the nail grows
- A stripe running the full length of the nail from the cuticle
- Several nails, fingernails included, changing at the same time, which points to a medicine or a whole-body cause
Antifungals will not touch a bruise, a stain or psoriasis, which is why the American Academy of Dermatology advises against antifungal tablets without confirming fungus first. More in is it just discoloration, or a fungal nail? If the skin between your toes is also peeling or itchy, see athlete's foot or something else.
How a Podiatrist Tells What Is Causing It
Looking is the start, not the answer. A visit usually covers:
- 1Every nail and the skin: all ten toenails, the skin between the toes, past injuries, polish habits and medicines.
- 2A nail clipping to the lab: painless, taken from the part of the affected area closest to the cuticle.
- 3A culture for a green nail, with a fungal test alongside.
- 4A biopsy for a worrying stripe: the only certain way to rule out melanoma.
How good the fungal tests are
| Test | What it shows | Detects fungus when present |
|---|---|---|
| Nail clipping with PAS stain | Fungal elements in the nail plate | About 81% to 92% |
| KOH microscopy | Fungal threads; quick and inexpensive | About 56% to 80% |
| Fungal culture | Which organism it is; slower than the others | About 23% to 85% |
| PCR | Fungal DNA | About 83% |
No test catches every case, so a negative result on a nail that still looks fungal may be repeated.
If You Have Diabetes or Poor Circulation
Both raise the risk of toenail fungus, diabetes makes it harder to clear, and with reduced feeling a thick nail can rub a sore you do not notice.
- •Have any new nail color change looked at, rather than watched for months
- •Do not dig under, file down or cut back a thick discolored nail yourself
- •Treat redness, swelling, warmth or drainage around a nail as same-day
See diabetic foot and wound care for how we look after higher-risk feet.
Whole nail black? Why Toenails Turn Black →
A dark dot, spot or stripe? Black Spot Under Toenail →
The toe itself is darkening? Toe Turning Black →
How long until a clear nail grows in? Toenail Regrowth Timeline →
Fungus that keeps returning? Why Toenail Fungus Keeps Coming Back →
Nail too thick or damaged to save? Toenail Removal for Fungus →
Frequently Asked Questions
What color is toenail fungus?
Most often yellow, brown or white, and sometimes orange, greenish black or black. The color usually starts at the tip or a side edge and spreads toward the cuticle as the nail thickens, crumbles and lifts. A chalky, powdery white surface is a separate superficial form. In darker skin tones a thick fungal nail often looks brown. Only a nail clipping test confirms it.
What causes discolored toenails that are not fungus?
Only about half of abnormal-looking nails turn out to be fungal. The rest include dark polish staining, blood under the nail from an injury or tight shoes, white spots from minor knocks, nail psoriasis, a usually harmless brown pigment stripe, green Pseudomonas bacteria and some medicines. A single nail after an injury, or a mark that grows out toward the tip, points away from fungus.
Can nail polish cause toenail discoloration?
Yes. Pigmented polish left on for a week or more can stain the nail, most often yellow or red. A dermatology review calls this harmless and says it fades in about two weeks once the polish is off; a base coat does not always prevent it. Removing polish can also leave chalky white patches called keratin granulations. A thick or crumbly nail is not staining.
Why are my toenails dark brown?
Dark brown toenails on several toes are most often fungus, which tends to look brown in darker skin tones, or staining from polish or dyes. Old blood under a nail also turns dark brown and grows out toward the tip. A brown stripe from the cuticle to the tip is usually harmless pigment, but a new, widening or single-nail stripe should be examined promptly.
What does a green toenail mean?
Usually green nail syndrome, an infection with Pseudomonas bacteria whose blue-green pigments stain the nail green-yellow, green-brown or green-black. It grows where the nail has lifted off its bed, often alongside fungus. It is often painless and not an emergency, but it needs treatment: trimming the lifted nail, keeping it dry, and antibiotic drops or tablets. Book sooner if you have diabetes.
When should I worry about a discolored toenail?
Get it checked promptly for a brown or black stripe that is new, widening, over 3 mm wide or on one nail; pigment spreading onto the surrounding skin; a lifting nail with pain, redness or pus; or thin red lines under the nails with a fever. Go the same day if the toe itself turns blue, grey or black. With diabetes or poor circulation, have any change checked.
How long does toenail discoloration take to go away?
It depends on the cause. Polish staining fades in about two weeks once the polish is off. Anything inside or under the nail, such as a white spot or old blood, has to grow out with it, and a toenail takes 12 to 18 months to grow out completely. With fungus, success shows as clear nail growing out from the cuticle, not a change at the tip.
Sources and further reading
- American Family Physician: Onychomycosis, rapid evidence review (2021)
- American Family Physician: Nail abnormalities, clues to systemic disease (2004)
- American Academy of Dermatology: Nail fungus, signs and symptoms
- American Academy of Dermatology: How to check your nails for melanoma
- Cleveland Clinic: White spots on nails (leukonychia)
- Cleveland Clinic: Subungual hematoma
- DermNet: Melanonychia
- DermNet: Drug-induced nail disease
- NHS: Peripheral arterial disease
- Rieder EA, Tosti A. Cosmetically induced disorders of the nail. J Clin Aesthet Dermatol (2016)
- Chiriac A et al. Chloronychia: green nail syndrome caused by Pseudomonas aeruginosa. Clin Interv Aging (2015)
- Vignes S, Baran R. Yellow nail syndrome: a review. Orphanet J Rare Dis (2017)
General patient education. Your examination and individual treatment instructions take priority.
See a Podiatrist Near You
ASG Foot & Ankle has offices in Homewood, South Chicago Heights and Mokena. Our board-certified podiatrists accept most insurance. Find the office closest to you:
Not Sure What Your Toenail Color Means?
One look, and a nail clipping test when it would change the plan, usually settles it. ASG Foot & Ankle can examine every nail, send a sample to the lab, check a stripe that needs a closer look, and treat fungus, green nail infections and painful thick nails.