Onychomycosis – A fungal infection that affects the fingernails or toenails.

Dermatophytids – An allergic reaction that occurs at a site other than the original fungal infection. The distant lesions are vesicles, or fluid-filled bumps, that can unite to form larger blisters. These skin lesions can be extremely uncomfortable or painful. Dermatophytids completely lack fungus.

Candida – A genus of fungus that can cause infection in several places in the body. The prototypical yeast infection is usually caused by a Candida species. Candida can cause a particular form of onychomycosis.

Trichophyton rubrum – Dermatophyte that is the most common cause of onychomycosis. It also causes athlete’s foot (tinea pedis) and jock itch (tinea cruris) among other tinea infections.

Tinea – Tinea is the name given to a fungal infection on the surface of the body. The name is combined with an anatomical location to describe the specific infection.
• Tinea capitis – Common dermatophytosis in children affecting the scalp.
• Tinea barbae – Involves the skin of the beard and coarse hairs of the face.
• Tinea faciei – Involves skin of the face unrelated to the beard area. Sometimes called “tinea incognito” because of its subtle appearance.
• Tinea corporis – Fungal infection of the body; also known as ringworm.
• Tinea manuum – Fungal infection of the hands (not nails, specifically).
• Tinea unguium – Fungal infection of the fingernails or toenails, a subset of onychomycosis.
• Tinea cruris – Fungal infection of the genital area; also known as jock itch.
• Tinea pedis – Fungal infection of the feet, usually starting in the toes; also known as athlete’s foot.

Candidal onychomycosis – Caused by Candida albicans and includes three subtypes: Candida paronychia, Candida onycholysis, and Candida granuloma. The only onychomycosis that is more common in women than men. Also occurs in the immunocompromised rather than in those with intact immune systems.

Proximal subungual onychomycosis – An uncommon form of onychomycosis in which the fungus infects the proximal nail fold through the cuticle and grows under and along with the nail. This type of onychomycosis usually only occurs in a patient that is immunocompromised in some way, such as by HIV infection, cancer, or chemotherapy.

White superficial onychomycosis – This form of onychomycosis stays near the topmost layers of the fingernail or toenail rather than growing under the nail. The infection forms a white, crumbly crust.

Distal subungual onychomycosis – The most common onychomycosis. Affects the fingernails and toenails at the tip. The infection is most often caused by Trichophyton rubrum. The infection grows underneath the nail mostly and causes streaks and pits, which can deform the nail.

Terbinafine – Marketed under the brand name Lamisil, this is a newer onychomycosis drug with activity against dermatophytes. It does not treat candidal onychomycosis. This drug is given orally over a period of four to twelve weeks.

Itraconazole – Marketed under the brand name Sporonox, this drug slows the growth of fungi. In addition to activity against dermatophytes it may also treat candidal onychomycosis. This drug is given orally for up to twelve weeks.

Ciclopirox – Topical drug that inhibits or kills fungal cells. More effective at treating onychomycosis when combined with a newer oral onychomycosis medication. Placed directly on the affected nail each day until symptoms resolve.

Amorolfine – Topical nail lacquer applied once or twice a week for the treatment of dermatophyte or candidal nail infection. Over-the-counter medication available without a prescription. Not available from pharmacies in the United States.

Tea tree oil – An herbal preparation with antifungal activity against dermatophytes and candida. Also known as Melaleuca alternifolia. Better able to treat fungal skin infections rather than fungal infections affecting the nails.

Athlete’s foot – A fungal infection of the feet, usually starting in the toes. Also called tinea pedis, this infection is commonly passed between persons sharing a common shower area.

Nail Bed – The tissue that is below the nail plate. It is the area on which the nail rests.

Nail plate – Hard sheet that is commonly thought of as the fingernail or toenail. Comprised mostly of keratin.

Antifungals – Medicines that can kill or inhibit fungi. Often used in the treatment of onychomycosis.

Keratin – Comprised mostly of protein, keratin exists in large quantities in hair and nails. Dermatophytes require keratin for survival, which explains their common sites of infection on the body.

Topical treatment – A treatment that is applied on the skin, and not administered orally or by any other route into the body. Topical treatments may absorb to a small degree through the skin, but they are usually intended to stay on the surface of the body.

Corneocytes – These are dead cells in the stratum corneum, which is the outermost layer of the epidermis. Corneocytes are filled with keratin.

Leukonychia – A situation in which there are white areas under the nail. This can be caused by several disease processes, including onychomycosis.

Hyperkeratosis – An abnormal thickening of the stratum corneum or outermost layer of the epidermis.

Onycholysis – A loosening of the fingernail or toenail though usually incomplete, so that it still remains attached.

Onychomadesis – Complete loss of the nail, usually to a disease that affects the entire body rather than a local infection. Severe onychomycosis can lead to onychomadesis.

Paronychia – Infection of the nail fold surrounding the nail plate which often produces swelling and redness. May also express pus. It is usually caused by a bacterial or fungal infection.