Introduction

Nail fungus is a very common problem. It usually develops on toenails, and in rare cases on the fingernails. Fungal nail infections are also referred to as “onychomycosis.”

Treatment is needed to get rid of fungal nail infections, and you will have to be patient. How long it takes for the fungus to go away completely also depends on how fast the nail grows. Toenails need more time than fingernails do.

At a glance

• Nail fungus usually causes the nails to become brittle or to turn a whitish-yellow or brownish color.
• It often affects the big toenails.
• Creams and medicinal nail polishes (varnishes) can be used to treat nail fungus, and you can also take tablets.
• Nail fungus is hard to get rid of. The treatment can take up to one year.

Symptoms

Whitish-yellowish or brownish discoloration of the nails is a sign of nail fungus. The nails may become brittle (crumbly), thicker or change their shape. Sometimes they hurt too. The affected part of the nail may detach from the nail bed.

The big toenails are often affected. The fungus typically affects the top part of the nail at the front or side edge. It is less common for the infection to start at the base of the nail.

Nail fungus on the big toenail – on light and dark skin

The infection can also cause white patches to form on the surface of the nail. They might remain as dots, but they may also spread out. This is called “white superficial onychomycosis.”

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 often occur on the fingernails.

A lot of people who have a nail fungus also have athlete’s foot. Because of this, experts believe that nail fungus is often caused by 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
• Damage to the nails, possibly caused by sports or nail care injuries
• Artificial fingernails
• Wearing tight shoes
• Certain skin conditions, such as psoriasis
• Circulation problems in the legs, for instance as a result of diabetes or peripheral artery disease (PAD)
• A weakened immune system, for example caused by a disease like HIV, or by taking medication that suppresses the immune system
• 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 because the immune system becomes weaker as we age.

Outlook

Fungal nail infections don’t usually have any serious consequences in people who are otherwise in good health, but they rarely go away on their own. Left untreated, the fungus can spread to the nail and destroy it. It’s not known how common that is, though.

Nail fungus can increase the risk of a bacterial infection of the surrounding skin in people with diabetes or a weakened immune system. The nail might also thicken, which can make it difficult to walk (for instance, if your shoe presses against the nail).

Diagnosis

It is sometimes hard to tell a fungal infection from other nail conditions. For example, psoriasis can also affect the nails and look like a fungal infection. There are various ways of testing the nail tissue. Your doctor may take a sample of the nail. which can be examined for fungal spores under a microscope. To find out which kind of fungus is causing the infection, though, a fungal culture needs to be grown from the sample. It may take up to three weeks for the results to come back.

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 fungus grows 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, especially between your toes
• Wearing shoes that aren’t too tight and let your feet breathe
• Not wearing the same pair of shoes for too long, and ideally changing them every other day
• Taking your shoes off as often as possible
• Wearing flip-flops when using swimming pools, communal showers and changing rooms
• Do not share shoes, towels or socks with others.

Damaged nails are more prone to nail fungus. Well-fitting shoes and socks that aren’t too tight can help to prevent injury to your toenails by reducing constant pressure when hiking or jogging or during longer walks.

Experts recommend washing socks, bedding and towels at 60 degrees Celsius (140 degrees Fahrenheit) or higher to prevent another fungal spore infection. There are also special products such as laundry sanitizers that kill fungal spores at low temperatures. The spores can survive for up to six months or longer in shoes, so they should be disinfected after any fungal infection.

There have not been any good-quality studies on how effective these recommendations are.

Treatment

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.

Tablets are often needed to get rid of a fungal nail infection. 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 infection. Tablets for treating infections of the toenails often have to be taken for at least three months. Fungal fingernail infections may only need to be treated for six weeks. The tablets may have side effects, such as stomach or bowel problems.

Further information

When people are ill or need medical advice, they usually go to see their family doctor first. Information about health care in Germany can help you to navigate the German healthcare system and find a suitable doctor. You can use this list of questions to prepare for your appointment.

Sources

• De Berker D. Clinical practice. Fungal nail disease. N Engl J Med 2009; 360(20): 2108-2116. [PubMed: 19439745]
• Deutsche Dermatologische Gesellschaft (DDG). S1-Leitlinie Onychomykose. AWMF- Registernr.: 013-003. 2022.
• Eisman S, Sinclair R. Fungal nail infection: diagnosis and management. BMJ 2014; 348: g1800. [PubMed: 24661991]
• Gupta AK, Daigle D, Foley KA. Network Meta-Analysis of Onychomycosis Treatments. Skin Appendage Disord 2015; 1(2): 74-81. [PMC free article: PMC4857825] [PubMed: 27170937]
• Gupta AK, Daigle D, Foley KA. Topical therapy for toenail onychomycosis: an evidence-based review. Am J Clin Dermatol 2014; 15(6): 489-502. [PubMed: 25257931]
• Kreijkamp-Kaspers S, Hawke K, Guo L et al. Oral antifungal medication for toenail onychomycosis. Cochrane Database Syst Rev 2017; (7): CD010031. [PMC free article: PMC6483327] [PubMed: 28707751]
• 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. [PMC free article: PMC3248359] [PubMed: 22136082]

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