The causes of uneven toenails with obvious demarcation line are nutritional deficiency, trauma and fungal infection. 1. Nutritional deficiency: If there is a lack of vitamins and trace elements, it will lead to a lack of nutrients for the growth of the nails, which will lead to uneven nails and lack of luster. 2. Trauma: when the nails are squeezed, damaged, etc., there will be damage to the nail bed, resulting in malnutrition of the nail plate. This causes the surface of the nail to be uneven, with demarcation lines and so on. 3. Fungal infection: the vast majority of cases is due to the feet sweat a lot, cleaning is not timely, resulting in fungal infection caused by the growth of nail fungus, will also be accompanied by blisters, itchy feet, foot odor and so on. If there are abnormal symptoms, you should consult a doctor in time.