if youre asking how do toenails become ingrown , the answer is usually , but not always , that the nail has been cut too short , or has broken before the end of the nail bed , and the part of the toe that extends beyond it has swollen , or risen above the level of the nail . the nail then grows , and rather than pushing the skin away which it would if just encountering the epidermis , andor dermis , the nail begins to grow though the skin . at this point all kinds of bacteria , dirt and other detritous get carried into the skin , causing inflammation andor infection , which further causes the skin to swell , and allows the nail to grow deeper into the skin . with a nail that has just started to ingrow , it ' s possible to train the nail to grow in the correct direction , by adding cotton wool below the nail , and then allowing it to grow over the skin . once it ' s started to penetrate , the only option is to cut the nail away , then treat the nail bed with phenol , which kills off the nail bed , turning it into regular skin .