Why Does Fingernail Polish Stain Nails?

When you use darker shades of polish, like deep reds, browns or purples. It's nothing to worry about and certainly is only a superficial effect. The polish is not harming your nails, so you can just go ahead and apply your new polish right over it. You can usually prevent the problem by using a base coat before your polish. L'Oréal makes a good one you can find in drugstores. Some manicurists swear that rubbing a lemon wedge over stained nails helps tone down the yellow. Give it a try, or just wait for the yellow to fade over time.