Nail fungus

Introduction

Photo of a man hiking outdoors
PantherMedia / Paul Simcock

If your nails become brittle or change color, it might be caused by a fungal nail . The big toenails are often affected. Nail fungus is less common on the fingernails.

Fungal nail infections are hard to get rid of. Because our toenails only grow slowly, treatment generally takes a long time and requires patience. It can take several months to work.

Symptoms

Whitish-yellowish or brownish discoloration of the nails is a sign of nail fungus. The nails may become brittle (crumbly), thicker and change shape. Sometimes they hurt too. The affected part of the nail may detach from the nail bed. Fungal nail infections are also referred to as "onychomycosis."

The big toenails are often affected. In the vast majority of people, the fungus develops at the front or side edge of the nail. It is less common for the to start at the base of the nail. This most commonly happens in people with a severely weakened – following a serious illness, for instance. It might also occur after an organ transplantation because people have to take medication that suppresses the .

Illustration: Nail fungus on the big toenail

Nail fungus on the big toenail

Sometimes the causes white patches to form on the surface of the nail instead. They might remain as dots, but they may also spread out. This is called "white superficial onychomycosis."

Illustration: White superficial onychomycosis on several toenails

White superficial onychomycosis on several toenails

Causes

Fungal nail infections are usually caused by fungi that infect the skin (dermatophytes). But they are sometimes caused by yeast or mold instead. Yeast infections usually occur on the fingernails.

A lot of people who have a nail fungus also have athlete's foot. Because of this, many experts think that nail fungus comes from athlete's foot.

Risk factors

There is no good-quality research into what might increase the risk of fungal nail infections. The following are thought to be risk factors:

  • Athlete's foot
  • Frequent contact with infectious fungi, for example in swimming pools and saunas
  • Damaged nails
  • Tight shoes
  • Certain skin conditions, such as psoriasis
  • Circulation problems in the legs, for instance as a result of diabetes or peripheral artery disease
  • A weakened immune system, for example caused by a disease like HIV, or by taking medication that suppresses the
  • A genetic predisposition

Nail fungus on the fingernails mainly occurs in people whose hands are often moist, like cleaning staff.

Prevalence

Nail fungus is very common. It is estimated that 3 to 12% of the population are affected. Older people are more likely to have it than younger people.

Outlook

Fungal nail infections don't usually have any serious consequences in people who are otherwise healthy, but they rarely go away on their own. If left untreated, the fungus may stay on just one part of the nail or it might spread out. It's not known how common that is, though.

Nail fungus can increase the risk of a bacterial of the surrounding skin in people with diabetes or a weakened . The nail might also thicken, which can make it difficult to walk.

Diagnosis

It's not always easy to tell a fungal from other nail conditions. For example, psoriasis can also affect the nails and look like a fungal . If doctors think that you may have a fungal nail , they may take a sample of the nail to be tested. A special dye can used to check the sample for fungal spores under a microscope. To find out which exact kind of fungus is causing the , though, a fungal culture needs to be grown from the sample. This can take about three weeks. Other – less common – tests are also an option, for example a closer examination of nail tissue in a laboratory.

Prevention

Nail fungus is believed to often develop as a result of athlete's foot, so preventing athlete's foot could also prevent nail fungus. Because fungi grow particularly well in damp surroundings, it's important to make sure you keep your feet dry. You could try the following, for example:

  • Drying your feet using both a towel and a hairdryer after showering, having a bath or swimming
  • Wearing shoes that aren't too tight and let your feet breathe
  • Not wearing the same pair of shoes two days in a row
  • Taking your shoes off as often as possible
  • Wearing flip-flops when using swimming pools, communal showers and changing rooms
  • Not sharing towels, shoes, or socks

Damaged nails can make you more prone to nail fungus. Well-fitting shoes and socks that aren't too tight can help to protect your toenails from constant pressure when walking or jogging for longer periods of time.

It's recommended that socks, bedding and towels be washed at 60 degrees Celsius or more to avoid another fungal spore . There are also special products such as laundry sanitizers that kill fungal spores at low temperatures.

But there haven't been any good-quality studies on how effective these preventive measures are.

Treatment

People often want to treat a fungal nail because they think it looks unpleasant. Treatment can also keep the nail from thickening and the from spreading.

Nail fungus can be treated topically (from the outside) with over-the-counter colorless nail polishes. They generally contain the ingredients amorolfine or ciclopirox. These substances stop the fungus from growing or kill it. They have to be applied regularly, sometimes for over a year. As well as nail polishes, there are also treatment sets that remove the infected part of the nail over two weeks. This involves using a urea-based cream to soften it first, and then scraping it off with a spatula. The skin beneath is then treated for a few weeks with a cream that contains the drug bifonazole.

Topical treatments aren't very effective. Tablets are usually needed to get rid of a fungal nail . They typically contain the drugs itraconazole or terbinafine. The choice of medication will depend on a number of factors, including what kind of fungus is causing the . The tablets usually have to be taken for at least three months to treat fungal toenail infections. Fungal fingernail infections may only need to be treated for six weeks. The tablets may have side effects, such as stomach or bowel problems. There's also a risk of liver damage, but that's very rare.

Further Information

When people are ill or need medical advice, they usually go to see their family doctor first. Read about how to find the right doctor, how to prepare for the appointment and what to remember.

De Berker D. Clinical practice. Fungal nail disease. N Engl J Med 2009; 360(20): 2108-2116.

Deutsche Dermatologische Gesellschaft (DDG), Deutschsprachige Mykologische Gesellschaft (DMykG). Tinea der freien Haut (S1-Leitlinie). AWMF-Registernr.: 013-002. October 2008.

Eisman S, Sinclair R. Fungal nail infection: diagnosis and management. BMJ 2014; 348: g1800.

Gupta AK, Daigle D, Foley KA. Network Meta-Analysis of Onychomycosis Treatments. Skin Appendage Disord 2015; 1(2): 74-81.

Gupta AK, Daigle D, Foley KA. Topical therapy for toenail onychomycosis: an evidence-based review. Am J Clin Dermatol 2014; 15(6): 489-502.

Kreijkamp-Kaspers S, Hawke K, Guo L, Kerin G, Bell-Syer SE, Magin P et al. Oral antifungal medication for toenail onychomycosis. Cochrane Database Syst Rev 2017; (7): CD010031.

Matricciani L, Talbot K, Jones S. Safety and efficacy of tinea pedis and onychomycosis treatment in people with diabetes: a systematic review. J Foot Ankle Res 2011; 4: 26.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Updated on June 14, 2018
Next planned update: 2021

Authors/Publishers:

Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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