Brown toenails most often come from fungus, injury, or staining, while a new dark streak can point to nail melanoma and needs prompt care.
A brown toenail can be harmless, annoying, or a sign that you should get seen. A few patterns, especially a new dark band on one nail, deserve quick attention.
What Causes Toenails To Turn Brown? Common triggers
When people ask what causes toenails to turn brown? they’re usually seeing one of three things: pigment inside the nail, a stain on the surface, or material under a nail that has lifted. The pattern tells the story: patch vs. streak, one nail vs. several, sudden vs. slow.
| Cause | What it tends to look like | Best next step |
|---|---|---|
| Fungal nail infection (onychomycosis) | Yellow-brown color, thickening, crumbly edge, debris under nail | Keep feet dry; get testing and treatment if it spreads |
| Bruise under the nail | Brown, purple, or black patch after a stub or tight shoes; grows out | Rest and protect; seek care fast if severe pain or lifting |
| Repeated shoe pressure | Brown spot near the tip or side, tenderness after long walks or runs | Fix friction and footwear; watch it move toward the tip |
| Nail polish or dye staining | Light brown or orange tone on the surface | Take a polish break; use a base coat next time |
| Nail psoriasis | Yellow-brown “oil drop” patch, pitting, lifting, rough surface | Dermatology visit; testing helps rule out fungus |
| Bacterial overgrowth with a lifted nail | Green-brown tint, moist gap under nail, odor | Keep dry; seek care if redness or swelling appears |
| Medication-related pigment change | Diffuse brown tone across several nails after a new drug | Bring it up at your next visit; don’t stop meds alone |
| Benign pigment band (melanonychia) | Thin, steady brown line that stays the same | Track with photos; get assessed if it changes |
| Nail melanoma | New dark band on one nail that widens or looks uneven | See a dermatologist soon |
If you have diabetes, nerve damage, poor blood flow, or a weak immune system, nail issues can turn into skin breaks and infections faster. Early care can save you trouble.
Fungal nail infection and yeast
Fungus is a common reason a toenail turns tan or brown and thick. It often starts at the edge, then moves toward the base. Warm, damp shoes and small cracks in the nail make it easier for fungus to take hold.
To see what typical fungal changes look like, read the NHS fungal nail infection guidance.
Clues that fit fungus
- More than one toenail is involved.
- The nail thickens and gets harder to clip.
- The edge turns ragged or crumbly.
- A lifted edge traps debris underneath.
Steps that help at home
Nails grow slowly. Even when treatment works, the nail often looks better only as new nail replaces the damaged part. These habits can slow spread and reduce breakage:
- Dry feet well after bathing, including between toes.
- Rotate shoes so each pair dries fully between wears.
- Clip straight across and file thick areas after a shower.
When you should get checked
Many nail problems mimic fungus. Testing can confirm it, and that can steer you toward the right treatment. Seek care sooner if the nail is painful, if redness spreads on the toe, if you see drainage, or if walking starts to hurt.
Injury and pressure from shoes
A brown or black patch that shows up after a stubbed toe is often dried blood under the nail. If it’s a bruise, it should drift toward the tip as the nail grows.
Bruise under the nail
In the first day, severe throbbing can mean pressure from pooled blood. Clinicians can relieve pressure safely in some cases. Don’t pierce the nail at home; burns and infections happen fast.
Micro-trauma from running and tight shoes
Long walks, hill runs, and snug toe boxes can repeatedly jam the nail. That can cause small bleeds and brown patches near the nail tip, often on the big toe or second toe.
Try a wider toe box, a half size up, and lacing that locks the heel back. If toes still hit the front, the fit isn’t right.
Stains from polish and dyes
Surface stains can make a nail look brown even when the nail itself is healthy. Dark polish, self-tanner, hair dye, and nicotine can tint keratin. The color sits on or in the top layers of the nail plate.
Quick check: wash the nail, then swipe rubbing alcohol on a cotton pad across the surface. If the pad picks up color, staining is likely.
To cut staining, use a base coat under dark polish and take a week off between polish cycles. Buff lightly if you buff at all.
Skin conditions that change nail growth
Some skin conditions change how the nail grows from the matrix under the cuticle. That can create brown patches, lifting, pitting, and rough texture.
Nail psoriasis
Psoriasis can cause a yellow-brown “oil drop” patch under the nail, plus pitting. Lifting is common, and that gap can trap debris that looks brown. If you already have psoriasis on the skin, the puzzle is easier. If you don’t, testing helps separate psoriasis from fungus.
Other inflammatory causes
Lichen planus and eczema can irritate the nail fold and change nail growth. These usually come with irritated skin, not just a color change.
Medicines and medical causes
Some medicines can darken nails by increasing pigment or leaving deposits in the nail plate. The change often shows across several nails and can begin weeks after a new medicine. Chemotherapy drugs, antimalarials, and some antibiotics are known triggers.
If the timing matches a new medicine, bring it up at your next appointment. Don’t stop a prescribed drug on your own.
When a brown nail needs fast attention
Most brown nails aren’t cancer. Still, nail melanoma can start as a brown or black streak, and delay can be costly. Treat a new, changing dark band like a “get it checked” sign.
The American Academy of Dermatology nail melanoma check page shows the nail changes dermatologists want you to watch.
Red flags that deserve a dermatologist visit
- A new brown or black band on one nail with no clear injury.
- A band that widens over time.
- Uneven color inside the band.
- Pigment that spreads onto the skin next to the nail.
- A nail that splits, cracks, or lifts in the same spot as the band.
- Bleeding, a lump under the nail, or recurring pain in the same nail.
Some people with darker skin have harmless pigment bands in nails. The pattern still matters. A new band that changes, especially on one nail, should be checked.
How clinicians find the cause
Most visits start with a close check of the nail plate, the skin around it, and the other nails. You may be asked about shoe fit, sports, polish use, recent injuries, and new medicines.
When fungus is suspected, a clipping or scraping can be tested. When a pigment band looks suspicious, dermoscopy can help, and a biopsy of the nail matrix may be needed to rule out melanoma.
What you can do today
Brown nails can feel like a guessing game. These steps help you narrow it down and track change.
Step 1: Map the pattern
- One nail or several?
- Patch, streak, or full-nail color change?
- Did it start after a stubbed toe, long walk, or new shoe?
Step 2: Take two photos
Take one photo straight on and one from the side. Use the same lighting each time. A monthly photo beats memory.
Step 3: Trim safely
Soak for 10 minutes, then dry well. Clip straight across. File only the thick, loose edge. Don’t dig into corners if you get ingrown nails.
| What you see | Likely match | Next step |
|---|---|---|
| Brown patch after impact that moves toward the tip | Bruise under the nail | Watch it grow out; seek care if pain is strong or nail lifts |
| Tan-to-brown color with a thick, crumbly edge | Fungal nail infection | Start dry-foot habits; get testing and treatment if it spreads |
| Light brown film that fades with polish breaks | Surface stain | Use base coat; let it grow out |
| Yellow-brown patch plus pitting or lifting | Nail psoriasis | Dermatology visit for diagnosis and treatment choices |
| Green-brown tint with a gap under the nail | Bacterial overgrowth with a lifted nail | Keep dry; seek care if redness, swelling, or pain shows |
| New dark band on one nail that widens or changes | Nail melanoma concern | Dermatologist visit soon |
| Diffuse brown tone across many nails after a new drug | Medication-related pigment | Raise it with the prescriber at the next visit |
| Brown nail plus open skin, pus, or spreading redness | Toe skin infection | Urgent medical care |
Keeping nails from turning brown again
You can’t prevent every cause, yet you can lower the odds of the common ones.
- Buy shoes with space for toes to wiggle, and retire pairs that pinch.
- Rotate shoes and let them dry between wears.
- Use clean tools and skip sharing nail gear.
- Use a base coat under dark polish and give nails rest days.
- Treat athlete’s foot early so it doesn’t spread to the nails.
Quick recap
If you’re still wondering what causes toenails to turn brown?, start with the pattern. Thickening and crumbling that starts at the tip often points to fungus. A patch after a stubbed toe often points to a bruise that grows out. A surface tint that fades with a polish break often points to staining.
Book a dermatology visit soon for a new, changing dark band on one nail, especially if it widens or darkens the skin by the nail. Getting that checked early is the safest call.
Mo Maruf
I created WellFizz to bridge the gap between vague wellness advice and actionable solutions. My mission is simple: to decode the research and give you practical tools you can actually use.
Beyond the data, I am a passionate traveler. I believe that stepping away from the screen to explore new environments is essential for mental clarity and physical vitality.