Onychomysosis is a fungal infection of the nail. Symptoms may include white or yellow nail discoloration, thickening of the nail, and separation of the nail from the nail bed. Toenails or fingernails may be affected, but it is more common for toenails. Complications may include cellulitis of the lower leg. A number of different types of fungus can cause onychomysosis , including dermatophytes. Risk factors include athlete's foot, other nail diseases, exposure to someone with the condition, peripheral vascular disease, and poor immune function.

The antifungal medication terbinafine taken by mouth appears to be the most effective but terbinafine is associated with the side effect of liver.

Onychomysosis occurs in about 10 percent of the adult population, with older people more frequently affected. Males are affected more often than females. Onychomysosis represents about half of nail disease. This means that the deformity of the toenails can also come from causes other than onychomycosis.

Treatment ― OTC Drugs
It is difficult to treat onychomycosis with topical medications because it is difficult for drugs to penetrate the thickened toenails.
#Butenafine [Lotrimin]

Long-term treatment is usually required until the infected toenail is completely removed out.
#Terbinafine (oral)
#Efinaconazole lacquer [Jublia]
#Ciclopirox lacquer
  • A toenail affected by Onychomysosis
  • A person's foot with a fungal nail infection ten weeks into a course of terbinafine oral medication. Note the band of healthy nail growth behind the remaining infected nails.
  • A case of fungal infection on the big toe.
References Onychomycosis: Current trends in diagnosis and treatment 24364524
Systemic antifungals are the most effective treatment. Meta-analyses shows mycotic cure rates as follows: terbinafine = 76%, itraconazole with pulse dosing = 63%, itraconazole with continuous dosing = 59%, fluconazole =48%. Concomitant nail debridement further increases cure rates. Topical therapy with ciclopirox is less effective; it has a failure rate exceeding 60%.
 Onychomycosis 28722883 
Onychomycosis is a fungal infection of the nail unit. When dermatophytes cause onychomycosis, this condition is called tinea unguium. The term onychomycosis encompasses the dermatophytes, yeasts, and saprophytic mold infections. An abnormal nail not caused by a fungal infection is a dystrophic nail. Onychomycosis can infect both fingernails and toenails, but onychomycosis of the toenail is much more prevalent. Discussed in detail in this activity are all evolving facets of the topic, including disease burden, clinical types, staging, diagnosis, and management of toenail onychomycosis. While non-life-threatening, onychomycosis can lead to severe complications such as cellulitis, sepsis, osteomyelitis, tissue damage, and nail loss.
 Terbinafine 31424802 
Terbinafine is an antifungal medication that works through the inhibition of squalene epoxidase. It has activity against most dermatophytes, and it has approval for use as an oral therapy for the treatment of onychomycosis. Although most side effects are mild and self-limited, such as headache and gastrointestinal symptoms, taste disturbances (dysgeusia) can range from mild to severe, resulting in weight loss, and have rarely been reported permanent.
 Onychomycosis: An Updated Review 31738146 
Onychomycosis is a fungal infection of the nail unit. Approximately 90% of toenail and 75% of fingernail onychomycosis are caused by dermatophytes, notably Trichophyton mentagrophytes and Trichophyton rubrum. Clinical manifestations include discoloration of the nail, subungual hyperkeratosis, onycholysis, and onychauxis. Currently, oral terbinafine is the treatment of choice, followed by oral itraconazole. In general, topical monotherapy can be considered for mild to moderate onychomycosis.