Nail Problems affect people of all ages. Common causes of nail problems include trauma, fungal or bacterial infection, weathering, chemical damage and skin diseases such as eczema and psoriasis. Nail changes may sometimes reflect internal medical problems, such as kidney or thyroid disease, anaemia or low albumin. Diet is generally not responsible for abnormal nail changes, unless the person is suffering from severe malnutrition. A rare but serious cause of nail changes is melanoma, an aggressive form of skin cancer that may present as a black band in the nail.