Vertical ridges are absolutely normal and is very common. It doesn't indicate any illness and is just due to aging. However, horizontal ridges sometimes may be the indication of some illness, but not always. Most commonly there may be interruption of nail growth due to nail matrix injury or nutritional deficiency that causes horizontal ridges and are usually harmless. Peeling off the nails may be due to long-term exposure to nail polish or some nutritional deficiencies. Besides these, certain systemic illness also causes horizontal ridges (especially when it is associated with depression, clubbing, thickening, brittle or any other deformities), so it wise to visit a dermatologist and confirm the cause.