9. Certain Medications Can Change Nail Color
Some medications can cause changes in nail pigmentation.
These changes may affect one nail or several nails and can appear as brown, gray, blue, or dark bands.
Certain chemotherapy drugs and other medications have been associated with nail pigmentation changes.
Some medicines may also contribute indirectly to nail problems by increasing sensitivity, causing nail separation, or affecting skin and nail growth.
However, medication-related pigmentation can resemble other conditions.
It is important not to assume that a dark toenail is harmless simply because someone takes prescription medication.
If a new nail change appears after starting a medication, discuss it with the prescribing clinician.
Do not stop prescribed treatment without professional guidance.
A healthcare professional can assess whether the medication may be responsible and determine whether additional investigation is needed.
10. Other Causes of Dark Toenails
In addition to the conditions already discussed, several less common factors may contribute to dark nail discoloration.
Bacterial infection
Certain bacteria can grow in damaged or separated nails.
Pseudomonas aeruginosa, for example, is associated with a greenish discoloration often called green nail syndrome.
Although the color is more commonly green or green-black than purely black, the appearance can sometimes be confusing.
A medical professional can determine whether an infection is present and recommend appropriate treatment.
Psoriasis
Nail psoriasis can cause pitting, thickening, discoloration, crumbling, and separation of the nail plate.
Some affected nails may develop unusual color changes.
People with psoriasis elsewhere on their skin may be more likely to experience nail involvement.
Repeated minor injuries
Even relatively small injuries can cause repeated bleeding beneath a nail.
This may happen during sports, walking, or activities involving repeated pressure on the toes.
The nail may gradually become darker or thicker.
Environmental staining
Certain dyes, nail products, chemicals, or external substances can stain the nail surface.
In these cases, the discoloration may be superficial rather than originating from beneath the nail.
If the dark area does not behave like an ordinary surface stain or cannot be explained, a medical examination is advisable.
How to Tell Whether a Black Toenail Is a Bruise or Something More Serious
Although appearance alone cannot establish a diagnosis, certain patterns may help identify what needs further evaluation.
| Feature | Possible traumatic bruise | Possible nail pigmentation or melanoma |
|---|---|---|
| History | Often follows an injury or repeated pressure | May appear without a clear injury |
| Appearance | Red, purple, brown, or black patch | Often a brown or black band or irregular patch |
| Development | Usually remains in the same relative position initially, then moves outward with nail growth | May gradually widen or change |
| Nail growth | Discolored area typically grows toward the tip | Pigmentation may continue to appear from the nail base |
| Surrounding skin | Usually unaffected | Pigment may extend onto surrounding skin |
| Pain | May be tender, especially after injury | Often painless in early stages |
These are general patterns, not diagnostic rules.
A traumatic bruise can look unusual, and melanoma can present in different ways. A dermatologist should assess suspicious or unexplained pigmentation.
What Should You Do If Your Toenail Turns Black?
The correct response depends on the suspected cause and the symptoms.
Step 1: Think about possible injuries
Consider whether you recently:
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Stubbed your toe.
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Dropped something on your foot.
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Wore tight shoes.
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Ran or walked a long distance.
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Participated in sports.
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Experienced repeated pressure on the nail.
A clear history of trauma makes a bruise more likely, although it does not rule out other conditions.
Step 2: Examine the nail carefully
Look for:
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The location of the dark area.
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Whether it is a patch or a longitudinal stripe.
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Changes in the width or shape.
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Swelling around the nail.
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Nail separation.
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Bleeding or discharge.
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Pigmentation extending onto surrounding skin.
Taking a photograph can help document changes over time.
However, photographs should not replace professional examination when warning signs are present.
Step 3: Protect the affected toe
If a minor injury is suspected:
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Avoid tight shoes.
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Wear comfortable footwear with enough toe space.
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Keep the foot clean and dry.
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Avoid pressure on the injured nail.
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Use a cold pack wrapped in cloth for short periods if swelling is present.
Do not place ice directly against the skin.
Step 4: Do not remove the nail yourself
A dark nail may eventually loosen and fall off, particularly after a significant injury.
Do not pull it off or attempt to remove it prematurely.
Removing a nail incorrectly can damage the nail bed and increase the risk of infection.
If the nail is severely damaged or detached, a healthcare professional can determine whether treatment is necessary.