Onychomycosis, also known as tinea unguium, is a skin disease caused by fungal infection of the nail plate and nail bed. It typically leads to symptoms such as yellowing nails, uneven surfaces, thickening, defects, and deformations. Following an infection, the nails can become damaged and incomplete, significantly affecting appearance. Furthermore, onychomycosis is contagious and can lead to other skin diseases, such as athlete's foot, ringworm, and jock itch. It can also lead to complications such as paronychia, causing pain and affecting walking, among other issues.