Some people have particularly curved toenails. When left untrimmed, there is pressure from the top of sides of the shoe that presses the toenail into the skin, causing discomfort, inflammation, and infection. Others have a toenail that folds over the end of the toe. As the toenail grows, the nail can grow into the end of the toe, again becoming painful and inflamed. In these cases, keeping the toenail trimmed regularly will be helpful in preventing a toenail from becoming ingrown.
It is beneficial for everyone to maintain their feet and toenails regularly. Long toenails can catch on shoes and socks, causing them to tear away. This is a very painful, and often bloody, situation. Trauma of this type can lead to infection, fungus infection, and permanent deformity of the toenail.