What Are the Causes of Brown Spots on Nails?

Updated April 17, 2017

Brown spots on fingernails or toenails can be caused by fungal infections, psoriasis, melanonychia striata or melanoma. If you notice nail discolouration that is not the result an injury, see a doctor.


Nails help to protect the tissue of your fingers and toes. Nails are composed mostly of keratin, a protein that exists in your hair and skin.

Fungal Infections

Fungal infections can cause brittle, crumbling, discoloured or thickening nails. Doctors often treat fungal infections with prescription antifungal medicines or removal of the nail.


Psoriasis is a chronic autoimmune skin disease that can cause brown spots on your nails. Your nails may also have dents on their surface.

Melanonychia Striata

Melanonychia striata are harmless dark lines on the nails caused by melanin, a pigment.


Brown spots on your nails could also be melanoma, or skin cancer.


Help prevent nail disorders by keeping your nails clean and dry, not biting your nails, wearing properly fitting shoes and trimming your toenails regularly.

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About the Author

Rebekah Richards is a professional writer with work published in the "Atlanta Journal-Constitution," "Brandeis University Law Journal" and online at She graduated magna cum laude from Brandeis University with bachelor's degrees in creative writing, English/American literature and international studies. Richards earned a master's degree at Carnegie Mellon University.