shany0702 Good day. There are various causes of horizontal dark lines across your nose. The most common are on the upper third and are due to a strong procerus muscle that can be corrected in mild cases with a neurotoxin injection like botox, xeomin or disport. Sometimes this is not enough and injections of a filler may be needed. In the worst cases a browlift maybe needed. If the horizontal line is in the lower third it may be due to allergy issues or a constant runny nose and drying that up along with treatment of the line is necessary. Sometimes they are due to trauma. Really, it all depends on your individual case. Please see a qualified plastic surgeon in your area to determine. If you can, include a photo and that will help us to assess your line. Good luck.