Nail fungus, also known as onychomycosis, is a condition that affects the nails of the hands and feet. It is caused by a fungus that grows in the nails and can cause discoloration, thickening, cracking, and splitting of the nails. It is a very common condition, affecting up to 10% of the population. The exact cause of nail fungus is not known, but it is thought to be caused by a combination of factors.
These include moist environments, such as showers and swimming pools, as well as exposure to warm and humid environments. Fungal nail infections can also be spread through direct contact with an infected person or object.