Toenail Fungus vs Melanoma: When a Dark Nail Needs Care
Short answer: Toenail fungus usually causes yellow, white or brown thickened nails. A new dark brown or black streak or band, especially if it widens, changes, or pigment spreads onto the skin beside the nail, needs a dermatologist’s opinion, because nail melanoma can look like fungus or a bruise. The AAD advises seeing a board-certified dermatologist for any nail change, including a new dark band. Do not wait or self-treat.
Key takeaways
- Most dark marks under a nail are not cancer, but a new dark streak or band should be looked at by a dermatologist, not watched for months.
- Signs the AAD lists include a dark brown or black band, darkened skin next to the nail, a lifting or splitting nail, and a bump under the nail.
- Fungus can darken a nail too, which is why looks cannot settle it: a clinician may examine, use a dermatoscope, take a sample or biopsy.
- This page has no treatment advice and no product links on purpose.
In this guide
Why this question matters
Searching “toenail fungus or melanoma” usually starts with a nail that looks wrong. Fungus is common; melanoma under the nail is rare but serious, and it can be mistaken for fungus, a bruise or a harmless streak. The reason to compare them is not to diagnose yourself. It is to know when a dark nail should not wait.
What the AAD says to look for
The American Academy of Dermatology lists these signs of melanoma in or under the nail (AAD: nail melanoma):
- A brown or black band (streak) in the nail, most often on the thumb or big toe, though any nail can show one.
- Darkened skin next to the nail, which may signal advanced melanoma.
- The nail lifting from the nail bed.
- The nail splitting down the middle.
- A bump or nodule under the nail.
- A color band that is wide and irregular, or dark and narrow.
The AAD says older adults and people with skin of color are more likely to develop it, and that a personal or family history of melanoma or previous nail trauma may raise risk. For any nail change, including a new dark band, it advises making an appointment with a board-certified dermatologist.
Other sources also describe pigment that spreads from the nail onto the surrounding skin (sometimes called Hutchinson’s sign) as a warning sign; see for example Columbia University Irving Medical Center.
What toenail fungus usually looks like
The AAD describes the first sign of nail fungus as a different color on part of a nail, with brittle nails, debris under the nail and lifting as other signs. The NHS describes nails that are brittle, discolored or thicker than usual, often starting at the edge and sometimes turning white or yellow (NHS). See our stage-by-stage guide and nail fungus color pages.
Fungus, bruise and melanoma compared
| Feature | Fungus | Bruise under the nail | Melanoma of the nail |
|---|---|---|---|
| Typical color | White, yellow, brown | Red, purple, brown or black | Brown or black band or spot |
| Pattern | Patch spreading, thickening, debris | Follows a knock; moves toward the tip as the nail grows | Streak or band that persists, widens or darkens; pigment may spread to skin |
| Pain | Often none early; pain later | Often sore at first | Often painless |
| What to do | Get tested, then treat with a clinician | If no knock or it does not move, get it checked | Get a dermatologist’s opinion promptly |
This table is a simplification. Real nails overlap, and a clinician has tools (such as a dermatoscope, and if needed a biopsy) that you do not. See also bruised toenail vs fungus.
What to do if you have a dark streak
- Book an appointment with a dermatologist or ask your GP or primary care clinician for a referral. Do not wait to see whether it goes away.
- Take a clear photo in daylight with a ruler or coin for scale, and note the date, so changes can be tracked.
- Do not apply home remedies, oils or nail polish to hide it, and do not pick at it.
- Tell the clinician about any injury, any past melanoma in you or your family, and any medicines.
- If a biopsy is suggested, ask what it involves and when results will be ready.
If a podiatrist is the first person you see, that is fine; they can refer you onward. See podiatrist or dermatologist.
Why people wait, and why that can be a problem
Dark streaks are easy to explain away. People assume a knock, a shoe that was too tight, or “just fungus”, and then wait for the nail to grow out. Some melanomas under the nail are painless and change slowly, which makes waiting feel safe. A bruise from a knock should move forward with the growing nail and fade; a streak that stays put, widens or darkens does not behave like that. If you cannot explain a dark mark with a clear injury, or it is not behaving like a bruise, a professional opinion is more useful than another month of watching.
There is also a reverse problem: people who have a confirmed fungal infection may assume any darkening is part of it. If a nail already diagnosed as fungal develops a new dark band, tell the clinician rather than assuming it is the same problem.
Keeping a simple record
Whatever the cause, a record helps the clinician. Note the date you first saw the change, which nail it affects, whether there was an injury, and whether it has grown, darkened or spread to the skin. A dated photo each month, in the same light, is enough. Do not try to measure it with home tools or use phone apps to judge risk. A photo is a memory aid, not a diagnosis.
Some people ask whether they should check all their nails. A reasonable habit is to look at hands and feet when you check your skin generally, including between the toes, and to mention new changes at routine appointments. This is general advice, not a screening schedule; your own clinician can tell you what suits your situation.
Can I have both?
Yes. A fungal infection can sit on a nail that also has another problem. That is another reason to avoid assuming. A fungal diagnosis based on a lab test does not rule out a second cause if a dark band persists or changes. Ask your clinician whether further checks are sensible.
Get prompt medical advice if
you notice a new dark brown or black streak or band in a nail, pigment spreading onto the skin next to the nail, a nail that lifts or splits without injury, a bump under the nail, or a nail wound that does not heal; if a dark nail is painful, bleeding or growing; or if you have a personal or family history of melanoma.
Questions to ask your doctor or clinician
- Does this dark band need a closer look or a biopsy?
- Could it be fungus, a bruise or something else, and how will we know?
- How often should we re-check it, and what changes should make me call sooner?
- Does my skin type or family history change how closely you want to watch it?
- Who should I see: a dermatologist, a podiatrist or both?
Frequently asked questions
How can I tell toenail fungus from melanoma?
You cannot reliably tell by looking. Fungus usually causes yellow, white or brown thickened nails, while melanoma can cause a dark band or spot. A clinician can examine the nail and test if needed.
Can toenail fungus look black?
Fungus and other infections can darken nails, which is why a dark nail still deserves a proper check, especially if the color is a streak or band.
Is a dark streak in the nail always cancer?
No, most are not. But the AAD advises seeing a board-certified dermatologist for any nail change, including a new dark band.
Who is more likely to get nail melanoma?
The AAD says older adults and people with skin of color are more likely to develop it, and a personal or family history of melanoma or previous nail trauma may raise risk.
Should I treat it as fungus first and wait?
No. A new dark band should not wait for a trial of home treatment. Get it examined first.
Related reading
- What does nail fungus look like?
- Bruised toenail vs fungus
- Nail fungus color: what it means
- Podiatrist or dermatologist for nail fungus
Sources
- AAD nail melanoma https://www.aad.org/public/diseases/skin-cancer/types/common/melanoma/nail-melanoma
- AAD nail fungus overview https://www.aad.org/public/diseases/a-z/nail-fungus-overview
- NHS fungal nail infection https://www.nhs.uk/conditions/fungal-nail-infection/
- Columbia University Irving Medical Center: melanoma signs and symptoms https://www.cancer.columbia.edu/cancer-types-care/types/melanoma/melanoma-signs-and-symptoms
Medical disclaimer. This page is general educational information, not medical advice, and it has not been reviewed by a doctor. It cannot diagnose your nail. Always talk to your doctor, podiatrist, dermatologist or pharmacist about your situation; see our medical disclaimer. Last reviewed by our editorial team: 20 October 2026.
