Toenail fungus is a medical condition that causes physical discomfort and pain and, often, psychological distress. Toenail fungus, medically termed “onchyomycosis”, begins as a cosmetic disfigurement but, without treatment, can evolve into a difficult-to-treat infection.

Who is Likely to Get Toenail Fungus?

Adults are particularly susceptible to toenail fungus, especially the elderly. Approximately 6 to 8 percent of the adult population has toenail fungus, while up to 90 percent of seniors are afflicted. Children rarely suffer from toenail fungus. About 2.6 percent of children will develop toenail fungus. An adult is 30 times more likely than a child to have the disease.

Toenail fungus affects people of all races, with men developing the infection more frequently than women. Toenail fungus is the most common toenail disorder and is responsible for half of all toenail disease.

Classes of Onychomycosis Fungi

Three classes of fungi cause Onychomycosis. The first class, dermatophytes, is responsible for 90 percent of toenail fungus. The second class, yeasts, causes 8 percent of onychomycosis and 2 percent originates from the third class, nondermatophytes.

Toenail Fungus Subtypes

There are several subtypes of toenail fungus. How toenail fungus manifests itself depends on which of the subtypes the infection belongs to.

The most common subtype, distal lateral subungual onychomycosis (DLSO), occurs when the fungus invades the bottom of the nail between the nail bed and causes inflammation. It accesses the nail by travelling over the skin.

The same process happens with endonyx onychomycosis (EO), where the fungi expand across the skin. The difference between DLSO and EO is the fungi invade the nail itself, rather than underneath the nail.

The least common subtype is proximal subungual onychomycosis (PSO). In PSO, the fungi invade the cuticle and fold of hard skin that overlaps the base and sides of the toenail (known as a “nail fold”) and then invade the nail.

A rare infection known as white superficial onychomycosis (WSO) happens when the fungi invade the nail surface and causes an infection of the nail bed.

Yeast infection toenail fungus has different characteristics than other subtypes. Yeast infections can make the nail separate from the nail bed or cause chronic mucous membrane disease of the nail and nail fold.

Dystrophic onychomycosis is not a subtype, but rather distinguishes any of the subtypes in its most severe form.

Fungi are more alike chemically and genetically to animals than other organisms, which makes treatment of fungal diseases lengthy and complicated.