Keep toenails clean and dry
Trim nails straight across
Wear properly fitting shoes
Change socks daily
Use antifungal treatment if fungus is the cause
Treat athlete’s foot promptly
Avoid repeated toe trauma
Stop using tight or high-pressure footwear
Let bruised nails grow out naturally
Seek medical care if the dark color is new, spreading, painful, or not improving
See a doctor if you have diabetes, poor circulation, or signs of infection
Get urgent evaluation if a dark streak appears without injury