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Onychomycosis (Fungal Nail Infection)

  1. What is onychomycosis?
  2. Symptoms
  3. Triggers
  4. Diagnosis
  5. Treatment
  6. FAQ

What is onychomycosis?

Onychomycosis (also known as tinea unguium) is a fungal infection affecting the toenails and fingernails, which occurs in about 10 percent of adults in the United States.[1] Onychomycosis more commonly affects toenails over fingernails.

The infected nail usually becomes thick and discoloured, a process which starts at the tip of the nail and progresses downwards towards the root. Infected nails may become crumbly, and it is not uncommon for part or all of the infected nail to break off. Treatment usually involves keeping the nail clean and taking a course of antimycotic (antifungal) medication.


The first signs of a fungal nail infection are usually perceptible changes to the appearance of the nail(s). It is uncommon for an infected nail to cause severe pain or permanent disfigurement, but this does occur in some cases. If left untreated, fungal nail infections can cause difficulties with walking, exercising or manual tasks such as typing. The main symptoms of onychomycosis include the nail becoming:

_ Brittle _ Broken _ Discoloured _ Thickened _ Flaky _ Lifted _ Painful _ Separated from the nail bed

These symptoms could also indicate that an individual is suffering from nail psoriasis, a chronic autoimmune skin disease which can affect the skin under the nail. Nail psoriasis is more common in the fingernails than the toenails and can co-occur with fungal infections of the nail.

Types of onychomycosis

Onychomycosis is usually caused by a buildup of dermatophyte fungi. These are parasitic fungi infecting the skin and nails, which need to reside in human or animal bodies in order to survive. Fungal infections of the nail are caused when dermatophytes burrow under the nails to breed.

Specific types of dermatophytes which commonly cause fungal nail infections include the trichophyton rubrum, the most common type of fungus to infect the nails, and trichophyton interdigitale fungi. Other fungi which can cause fungal nail infections include yeasts, such as the candida albicans and molds, such as scopulariopsis brevicaulis.

The rarest form of fungal nail infection is called proximal subungual onychomycosis. Infection usually involves the trichophyton rubrum fungus and occurs, initially, at the proximal nail fold (the base of the nail), spreading up the newly developed nail plate. This form of infection usually occurs in people whose immune system is compromised. Proximal subungual onychomycosis is a clinical marker for human immunodeficiency virus (HIV).[2]


Wearing tight-fitting socks and shoes, which cause repetitive trauma to the toenails, is a primary cause of fungal nail infections. Onychomycosis is therefore common in people who play a lot of sport, as well as the elderly and anyone with a compromised immune system.

Moist, damp environments serve as breeding grounds for dermatophytes. Healthy people typically catch nail infections from visiting places such as:

  • Communal showers
  • Nail salons and foot spas with inadequately cleaned instruments
  • Public swimming pools, jacuzzis and saunas


If somebody is suffering from a suspected fungal nail infection, it is advisable to visit the doctor so that they can advise on a treatment plan for the infected nail(s). Fungal nail infections are diagnosed based on the visible symptoms.

Samples of nail clippings are usually sent away for a histopathology examination, the analysis of diseased tissue, in order to identify the presence of dermatophytes and decide on appropriate medication. There is a 30 percent possibility of false negatives when testing for dermatophyte cultures, so it is possible that the test may need to be repeated.[3]


Fungal nail infections do not get better spontaneously, so a course of treatment is always required. This usually involves a combined approach of keeping the affected nails clean to reduce irritation and inflammation, at the same time as following a course of antifungal medication. Onychomycosis is highly infectious, so it is important to begin treatment as soon as possible to minimise the risk of passing the infection to others.

Prevention and management

There are various precautions that one can take in order to reduce the risk of spreading fungal nail infections to others and to increase the chances of a quick recovery. To look after one’s nails and prevent the spread of infection, it is recommended to:

  • Change one’s socks and shoes regularly
  • Dry one’s hands and feet as soon as possible after exposure to water
  • File one’s nails to keep the edges smooth
  • Moisturise one’s hands, nails and cuticles daily and after contact with liquids
  • Select shoes and socks made of natural materials, such as cotton
  • Treat skin infections like Athlete’s Foot promptly to avoid the infection reaching the nails
  • Trim nails regularly
  • Use separate scissors or clippers to tend to infected nails
  • Wear clean, comfortable shoes
  • Wear gloves for housework and other manual tasks


In addition to keeping the site of the infection clean, someone affected by a fungal nail infection may be prescribed topical antimycotics, i.e.antifungal products to apply to the affected area. Topical medications are currently the first-line treatment for fungal nail infections.[3]

Topical medications used to treat fungal nail infections include:

  • Amorolfine nail lacquer
  • Tioconazole nail solution
  • Ciclopirox

Always use topical antifungal products according to a doctor’s advice and/or follow the guidelines on the packet.

In some cases, all or part of the infected nail may be removed, in order to give the topical medications the best chance to work. This treatment is usually recommended for severe or persistent nail infections. It can be carried out during a regular appointment at the doctor’s office. If the nail is removed surgically, a local anaesthetic will be applied to the affected area to ensure that the affected person will not feel pain, before the infected part of the nail is removed using a tool.[4]

An advantage of surgical removal is that it can be carried out in one appointment, and then the course of topical antimycotic medication can be started. Alternatively, a dressing containing urea can be applied to the affected nail. This must be kept dry for 10 days, during which time the urea will soften the nail, so that it can be removed painlessly by the doctor during a follow-up appointment.

After the nail is removed, if this is needed, topical medications can then be applied with best results. The infection is considered to have cleared up when the new, healthy nail starts to show visible regrowth in the nail bed.

Medications that can be applied directly to the affected area are the first-line treatment for fungal nail infections, primarily because they do not carry the risk of having the side effects that can accompany the use of oral antifungal medications (medications designed to be swallowed), which include:[5]

  • Itching
  • Headaches
  • Diarrhea
  • A decreased sense of taste

Courses of oral antimycotics for fungal nail infections typically last for between 6 and 12 weeks, allowing enough time for a healthy nail to grow and replace the infected one. The most common oral antimycotics for onychomycosis are itraconazole and terbinafine, which work by gradually killing the fungi that caused the infection.

The doctor will assess a person’s medical history before prescribing these medications, as they may not be suitable for everyone. People who have had liver problems should avoid terbinafine. Itraconazole has been linked to compromised heart function and may react with other medications, including pimozide, quinidine, dofetilide and levacetylmethadol (levomethadyl).

Onychomycosis FAQs

Q: Is it always possible to cure onychomycosis?
A: Onychomycosis can take a long time to treat, and some fungal nail infections can be resistant to antifungal medications. Treating a fungal nail infection can depend on identifying the appropriate medication that is effective against a particular subtype of infection.

Q: Can nail polish cause onychomycosis?
A: Nail polish is a sealant, so it can cause a buildup of moisture behind the nail, potentially creating an environment in which dermatophytes and other microorganisms can thrive. Avoiding nail polish is recommended while undergoing treatment for onychomycosis, as it could reduce the effectiveness of the antifungal medication. Furthermore, the applicator brush could be a vehicle for spreading infectious microorganisms.

Q: What are the main methods for removing a fungal nail?
A: Fungal nails can be removed surgically, using a tool to loosen the skin around the nail and remove the nail after a local anaesthetic is applied to the affected area to prevent pain. If the whole nail is removed, this is called avulsion. If part of the nail is removed, this is called debridement.

Alternatively, the nail can be removed chemically (non-surgically) by placing a dressing containing urea on the nail. This must be kept dry for 10 days after which the nail is softened to the point where it can be removed painlessly by the doctor.

Good to know: It is also possible to treat a fungal nail infection by removing the infected nail using a laser. Laser treatment for onychomycosis is not usually considered, other than in cases where antifungal medication has been ineffective.

  1. Onychomycosis: Current trends in diagnosis and treatment.” American Family Physician. December 2013.

  2. Treating Onychomycosis.” American Family Physician. February 2001.

  3. Fungal infections of the nails.” British Association of Dermatologists. July 2017. Accessed: 15 March 2018.

  4. Surgical nail removal for fungal nail infections.” Cigna. 05 February 2016. Accessed: 15 March 2018.

  5. Fungal nail infection.” NHS Choices. 19 December 2017. Accessed: 15 March 2018.