Introduction to Fungal Nails (Onychomycosis, Tinea Unguium)
Many changes in fingernails or toenails may cause people to think they have a fungal infection of the nails, medically known as onychomycosis.
Fungal infection of the nails sometimes makes the condition sound contagious or related to poor hygiene. In fact, up to 10% of all adults in Western countries have fungal infection of the nails. This percentage increases to 20% of adults who are age 60 or older.
In reality, abnormal-looking nails may be caused by a number of conditions including, but not limited to, fungal infection. There are many other reasons why your nails may look different.
Source: http://www.rxlist.com