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 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 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.