80% of the women’s feet I see, are wearing polish on their toenails. Unlike fingernail polish which rarely lasts more than a week, toenail polish is often left on for weeks at a time, sometimes until it wears off completely. Toenails need air to thrive and prolonged toenail polish can cause a surface type of fungus to inhabit.
These are pictures of surface toenail polish fungus, before and after the coarse side of an emery board files it away. If left unchecked, it can contribute to a worse type of fungus which can’t be filed away.