Fungal Nail Infections Causes, Symptoms and Treatment
Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines. You may find the Fungal Nail Infections (Tinea Unguium) article more useful, or one of our other health articles.
Treatment of almost all medical conditions has been affected by the COVID-19 pandemic. NICE has issued rapid update guidelines in relation to many of these. This guidance is changing frequently. Please visit https://www.nice.org.uk/covid-19 to see if there is temporary guidance issued by NICE in relation to the management of this condition, which may vary from the information given below.
Synonyms: onychomycosis, tinea unguium
What are fungal nail infections?
Different fungal organisms may infect the nails, with different patterns of presentation, affecting any part of the nail from the nail bed to the nail matrix and plate. The most common result is a poor cosmetic appearance of the affected nail(s); however, the condition may also cause pain, disfigurement and functional impairment.
Whilst not life-threatening, quality of life may be impaired through feelings of stigmatisation (comparable to other skin diseases) and the avoidance of certain activities - eg, swimming or other sports involving communal changing rooms.
How common are fungal nail infections? (Epidemiology)
This is one of the most commonly occurring dermatological conditions. International prevalence reports a range from 3-26% worldwide. UK prevalence studies report a range of 3-8% in the UK. The incidence of new cases of onychomycosis (OM) appears to be rising due to the increasing prevalence of diabetes in the population, more frequent incidence of immunosuppression and an ageing population.
Risk factors for fungal nail infections
- Age - adults are ~30 times more likely than children to suffer the condition. It affects 2.6% of children younger than 18 years. The figure in people over 60 is nearer 20%.
- Immunosuppression - illness or medications that suppress immune responses greatly increase the likelihood of developing OM.
- Diabetes mellitus - one study found that clinical onychomycosis was found in 162 of 321 patients with type 2 diabetes mellitus.
- Cutaneous fungal infection co-exists with OM in about 30% of cases.
- Living in a warm, humid climate.
- Participation in athletic/sporting activities, regular communal bathing and occlusive footwear.
- Prior trauma to the nail.
Infecting organisms[2, 9]
- Trichophyton rubrum or Trichophyton mentagrophytes causes over 90% of cases. T. rubrum is responsible for about 70% of the total.
- Other organisms in this group include Epidermophyton spp. and Microsporum spp.
These cause ~8% of total infections, particularly Candida albicans in the UK and Malassezia furfur (called Pityrosporum orbiculare in its yeast-like form) in tropical climes.
These cause about 1-10% of total infections in the general population - eg, Scopulariopsis brevicaulis. However, they are the predominant causative organisms in patients who also have HIV.
Fungal nail infection symptoms[2, 13]
The toenails are affected in about 80% of cases of OM.
By James Heilman, MD, CC BY-SA 3.0, via Wikimedia Commons
Distal and lateral subungual onychomycosis (DLSO)
DLSO form the vast majority of cases of OM:
- Nearly always caused by dermatophytes.
- Can either affect a healthy nail or one already diseased - eg, by psoriasis.
- Affect the hyponychium (epithelium of nail bed), often at the lateral edges initially.
- Spread proximally along the nail bed, causing creamy/buff discolouration, subungual hyperkeratosis and onycholysis.
- The nail plate is not affected initially but may become so in time.
- May be confined to one side of the nail or spread sideways to involve the whole nail bed.
- Relentless progression until it reaches the posterior nail fold. Progression can occur within weeks or more slowly over months or years with the nail becoming opaque, thickened and cracked, friable and raised from the nail bed.
- The nail plate becomes friable and may disintegrate, particularly after trauma.
- Surrounding skin is nearly always affected by tinea pedis.
- Approximately 80% of cases occur on the feet, especially on big toes, often affecting both toenails and fingernails. Fingernail DLSO has a similar appearance although nail thickening is less common; toenail infection usually precedes it.
Superficial white onychomycosis (SWO)
SWO is less common than DLSO:
- It is usually due to dermatophyte infection with T. mentagrophytes.
- It presents as white chalky plaque on the proximal nail plate, almost exclusively on the toenails.
- The surface of the nail plate is affected rather than the nail bed. The nail plate may become eroded and even lost.
- There is white rather than creamy discolouration.
- There is a notably flaky surface on the nail plate.
- Onycholysis is not usually a feature.
- Concurrent tinea pedis is less common than in DLSO.
Proximal subungual onychomycosis (PSO)
PSO is uncommon:
- Candidal OM occurs in three different types:
- Candidal paronychia: initially appears as oedema, erythema and pain of the nail fold, from which pus can be expressed at times. Also, the nail plate becomes dystrophic with patches of opacification or discolouration (white, yellow, green or black) with transverse furrows. Usually, pressure on the nail causes pain. Most cases are on fingernails - usually the middle finger.
- Subungual abscess with DLSO occurring in the setting of onycholysis.
- Total nail dystrophy: affects all or a large proportion of nails, associated with chronic mucocutaneous candidiasis (CMC). The entire fingernail may become thickened and dystrophic.
- Causes chronic paronychia with secondary nail dystrophy.
- May affect the distal nail alone without paronychial involvement (usually in cases of Raynaud's phenomenon or peripheral arterial disease).
- Usually affects fingernails without toenail involvement in those whose occupations cause them constantly to have wet or allergen-irritated hands.
- Cuticular detachment and signs of infection and inflammation in the nail matrix may be observed.
- May complicate CMC or as a secondary infection due to other causes of nail disease - eg, psoriasis.
Total dystrophic onychomycosis (TDO)
- Represents a long-standing, severe, end-stage disease progressing from all the above clinical patterns.
- Complete destruction of the nail plate is observed.
- Although at least 50% of cases of nail destruction are due to fungal infection, it is not possible to identify the cause of nail disease clinically.
- Microbiological confirmation of the diagnosis is necessary before starting antifungal therapy, as it is relatively toxic and needs to be administered for long periods.
- The use of a Wood's UV lamp is not helpful in detecting fungal disease of the nails.
Differential diagnosis[2, 12]
Only about 50% of discoloured or dystrophic-appearing nails have a fungal infection confirmed with dermatophyte on culture. Other causes include:
- Onychogryphosis (thickening and distortion of the nail, typically of the big toe, thought to be due to previous nail bed trauma).
- Trauma (tight shoes, nail biting).
- Poor foot care.
- Eczema (irritant or allergic contact dermatitis).
- Lichen planus.
- Subungual melanoma.
- Psoriatic nail disease.
- Bacterial paronychia - eg, Pseudomonas spp. infection.
- Systemic disease - eg, thyroid disease, diabetes, peripheral arterial disease.
- Rare systemic disorders - eg, keratosis follicularis (Darier's disease), yellow nail syndrome, nail-patella syndrome, pachyonychia congenita.
- Idiosyncratic drug reaction (especially tetracyclines, quinolones and psoralens).
Testing for infection is not needed if treatment would not be given.
- Nail material should be sent for microscopy. There is a high false negative rate (30-40%) and even positive results should be interpreted with caution, as fungal organisms may exist as saprophytes, rather than as an invasive infection.
- Culture of nail material should also be undertaken, as this increases sensitivity and will determine species but may take several weeks.
- Nail histology is not usually necessary unless there is reason to suspect another cause of nail pathology, such as psoriasis.
- Polymerase chain reaction is an effective method of detecting dermatophytes but is not used in routine practice.
Interpretation of results
Microscopy results take a few days but culture results may take 4-6 weeks. The results are regarded as positive:
- For dermatophytes, if either microscopy or culture is positive.
- For Candida spp., if both microscopy and culture are positive.
- For non-dermatophytes, if both microscopy and culture are positive on at least two samples taken at different times. Non-dermatophyte moulds are rare causes of nail infection (usually secondary infection following trauma or an underlying dermatophyte infection).
- Subungual material from the most proximal part of the infection will give the highest yield, as this is where the maximal concentration of hyphae is found.
- In DLSO, use a small dental scraper or similar instrument to obtain a specimen from beneath the nail plate.
- In onycholytic nails, cut them back to the most proximal point that can be attained and take a subungual sample and nail-bed sample.
- Send the laboratory as much material as possible.
- In SWO, use a scalpel to scrape friable material off the surface of the nail.
- in PSO, use a scalpel blade to scrape away material from the proximal nail fold or perform punch biopsy to include material from nail bed.
Associated diseases[2, 16]
- Diabetes mellitus.
- Any cause of immunocompromise.
- Raynaud's phenomenon.
- Peripheral arterial disease.
- Tinea pedis.
- Occupational dermatitis of hands.
- Nail trauma.
Fungal nail infection treatment and management[8, 14, 16]
To treat or not to treat?
There is no need to treat if the person is not worried about the appearance, there are no symptoms and no comorbidities which could increase the risk of complications.
- Patients should be given the information to make an informed decision based on:
- Even after successful treatment of the fungal infection, the nail may not look completely normal.
- Cure is not achieved in 20-40% of patients.
- Even in those in whom it is successful, nails may appear abnormal for over 12 months due to their slow growth.
- Relapse occurs in about 20-25% of people.
- Oral medication is taken for six weeks for fingernail infections and for three months for toenail infections.
- Topical treatments may need to be applied for up to 12 months.
- All medication has potential side-effects.
- However, anyone who presents should probably be offered treatment, as the condition is likely to be causing significant distress if it has brought them to consult.
- If the condition progresses, it can cause significant morbidity and functional disturbance, particularly in the elderly.
- There is also a public health argument for treating it, to lessen the reservoir of fungal spores in communal bathing areas, through reduction in the number of people with the condition.
Referral to a chiropodist may be helpful.
- Nail filing and nail polish can lessen cosmetic effects.
- It is helpful to trim dystrophic nails.
- In DLSO, remove nail and hyperkeratotic nail bed with clippers.
- In SWO debride abnormal nail with a curette.
- Nails should be trimmed short.
- Non-occlusive footwear should be worn, without high heels or narrow toes. Consider replacing old footwear which could be contaminated..
- Wear cotton, absorbent socks.
- Good foot hygiene is important.
- Protective footwear should be worn in communal areas - eg, changing rooms, and gyms - to avoid re-exposure.
- Avoid prolonged or frequent exposure to warm, damp conditions if possible.
- Avoid trauma to the nails if possible.
In general, topical treatments are slightly better than placebo but often fail due to poor penetration of the nail plate.
- They should be reserved for mild distal disease in up to two nails, where there is up to 50% involvement of the nail matrix, or for SWO, or where there are contra-indications to systemic therapy.
- Treatment should be given daily for 6-9 months for fingernails and one year for toenails .
- Can be used in cases of SWO or early DLSO where infection is confined to the distal edge of the nail.
- Commercial nail varnish or false nails should be avoided.
- 5% amorolfine is effective and appears to be the best topical agent in terms of its ability to penetrate the nail matrix.
- Evidence for combination treatment with oral and topical antifungals may be considered if topical treatment alone is ineffective .
- Methods using techniques to improve the transmission of topical drugs across the nail bed, such as iontophoresis, are being researched.
Systemic therapy[14, 16]
Systemic treatment is recommended if topical treatment fails or is contra-indicated. The slow growth of nails means that they do not appear normal even after effective treatment.
If dermatophyte nail infection is confirmed
- Currently first-line with evidence of greater efficacy compared to itraconazole.
- Prescribe 250 mg once a day for between six weeks and three months for fingernails, and for three to six months for toenails.
- Advise the person that visible improvement may be seen after the end of two months of fingernail treatment and three months of toenail treatment.
- It is not licensed for use in children.
- There have been cases of severe idiosyncratic skin and hepatotoxic reactions.
- It interacts with rifampicin and cimetidine.
- Should be offered if an alternative to terbinafine is indicated.
- Highly active against Candida spp. but much less so against dermatophytes.
- It can be given in a pulsed rather than continuous regimen. 200 mg twice a day for one week, with subsequent courses repeated after a further 21 days.
- Prescribe two pulses for fingernails and three pulses for toenails.
- It can cause hepatotoxicity and LFTs should be checked for treatment lasting longer than a month.
- It is contra-indicated in pregnancy and not licensed for use in children.
- It interacts with a wide variety of commonly used pharmaceutical agents, including warfarin, antihistamines, antipsychotics, digoxin, H2-receptor antagonists, some statins and phenytoin.
If terbinafine and itraconazole are contra-indicated, consider using griseofulvin.
- May be used in adults and children.
- It is not expensive and there is a long experience of its use.
- It requires long duration of treatment (at least six months) and has low cure and high relapse rates.
- It interacts with warfarin, ciclosporin and the combined oral contraceptive pill (it is an hepatic enzyme inducer).
- Fluconazole is not licensed for this use and is not as effective as terbinafine or itraconazole. However, it may have a role in patients in whom other alternatives are not tolerated, have unacceptable dosage regimes or cause adverse effects.
- Side-effects of systemic antifungals include headache, itching, loss of sensation of taste, gastrointestinal symptoms, rash, fatigue and abnormal liver function.
- One meta-analysis looking at safety of antifungals used to treat superficial fungal infections found a low incidence of adverse events in an immunocompetent population. The risk of having asymptomatic serum transaminase elevation which did not require treatment discontinuation was less than 2.0% for all treatment regimens. The risk of an adverse liver reaction requiring treatment to be stopped ranged from 0.1% (continuous itraconazole) to 1.2% (continuous fluconazole).
If candidal or non-dermatophyte nail infection is confirmed
Use itraconazole first-line, terbinafine second-line and griseofulvin third-line.
- Manage any comorbidities which may be hampering the effectiveness of treatment.
- Consider re-investigating the cause.
- Consider referral to a podiatrist.
Nail avulsion, removal of nail plate, chemical treatments (eg, 40-50% urea solution for very thickened nails) and matrixectomy may enhance the effectiveness of oral treatment.
Studies are reporting the successful use of laser treatment but a Cochrane review recommended further research.
- Diagnostic uncertainty remains.
- There is no response to medical treatment.
- The patient's choice is to have surgical intervention.
- Children are concerned - it is a rarer condition in children compared to adults and there are more limited treatment options.
- There is suspected immune deficiency - eg, mucocutaneous candidiasis.
- There is extensive disease.
- There are recurring candidal nail infections.
- Poor cosmetic appearance of hands/feet.
- Disfigurement and total destruction of the nail plate.
- Damage to diabetic feet.
- Cellulitis, osteomyelitis, sepsis and necrosis in elderly patients and people with diabetes.
- Psychosocial problems due to embarrassment at cosmetic appearance.
- Pain and limitation of function, particularly in older patients.
- The prognosis is variable and depends on the type of infection as well as host factors such as comorbidities and age. Meta-analyses report mycotic cure rates of of 76% for terbinafine, 63% for itraconazole with pulse dosing, 59% for itraconazole with continuous dosing and 48% for fluconazole.There is often a discrepancy in clinical and microbiological cure rates in clinical trials[15, 24]. Cure, as defined by successful eradication of fungus on microscopy and culture, will not always result in a normal appearance of the affected nail due to:
- Delay of 6-12 months as the damaged nail grows out.
- The nail possibly having been dystrophic to begin with, predisposing it to fungal infection.
- Fingernail infections usually have much higher cure rates, in the region of 70%.
- Untreated, fungal nail disease is usually progressive, leading to gradual destruction of the nail plate. However, there may be cases that spontaneously remit that do not present to their doctor.
Fungal nail infection prevention
Primary prevention is not practised, except where there is a cause of immunocompromise, such as AIDS, where prophylactic therapy may be considered.
Secondary prevention with topical terbinafine cream after cure with systemic terbinafine appears to be effective in reducing relapse rates.
Suggested hygiene measures to limit spread and prevent relapse include:
- Treating other fungal infections, such as athlete's foot.
- Wearing footwear in public environments such as communal bathing places, locker rooms and gymnasiums.
- Replacing old footwear, as this could be contaminated with fungal spores.
- Keeping the area clean, drying well after bathing, changing socks regularly.
- Avoiding trauma to the nails.
- Avoidance of towel sharing.
- Avoidance of repeated hand washing/immersion of the hands in water if the fingernails are affected.
- Wearing sandals or slippers in communal bathing places, locker rooms, gyms, etc.
Further reading and references
Eisman S, Sinclair R; Fungal nail infection: diagnosis and management. BMJ. 2014 Mar 24348:g1800. doi: 10.1136/bmj.g1800.
Hwang SM, Suh MK, Ha GY; Onychomycosis due to nondermatophytic molds. Ann Dermatol. 2012 May24(2):175-80. Epub 2012 Apr 26.
Szepietowski JC, Reich A; Stigmatisation in onychomycosis patients: a population-based study. Mycoses. 2008 Sep 12.
Grover C, Khurana A; Onychomycosis: newer insights in pathogenesis and diagnosis. Indian J Dermatol Venereol Leprol. 2012 May-Jun78(3):263-70.
Shahzad M, Alzolibani AA, Robaee AA, et al; Onychomycosis in qassim region of saudi arabia: a clinicoaetiologic correlation. J Clin Diagn Res. 2014 Aug8(8):YC01-4. doi: 10.7860/JCDR/2014/8277.4757. Epub 2014 Aug 20.
Rosen T, Friedlander SF, Kircik L, et al; Onychomycosis: epidemiology, diagnosis, and treatment in a changing landscape. J Drugs Dermatol. 2015 Mar14(3):223-33.
Kim DM, Suh MK, Ha GY; Onychomycosis in children: an experience of 59 cases. Ann Dermatol. 2013 Aug25(3):327-34. doi: 10.5021/ad.2013.25.3.327. Epub 2013 Aug 13.
Loo DS; Onychomycosis in the elderly: drug treatment options. Drugs Aging. 200724(4):293-302.
Gulcan A et al; Prevalence of toenail onychomycosis in patients with type 2 diabetes mellitus and evaluation of risk factors. J Am Podiatr Med Assoc. 2011 Jan-Feb101(1):49-54.
Leelavathi M, Noorlaily M; Onychomycosis nailed. Malays Fam Physician. 2014 Apr 309(1):2-7. eCollection 2014.
Ataides FS, Chaul MH, El Essal FE, et al; Antifungal susceptibility patterns of yeasts and filamentous fungi isolated from nail infection. J Eur Acad Dermatol Venereol. 2012 Dec26(12):1479-85. doi: 10.1111/j.1468-3083.2011.04315.x. Epub 2011 Nov 3.
Hoy NY, Leung AK, Metelitsa AI, et al; New concepts in median nail dystrophy, onychomycosis, and hand, foot, and mouth disease nail pathology. ISRN Dermatol. 20122012:680163. Epub 2012 Jan 26.
Lee MH, Hwang SM, Suh MK, et al; Onychomycosis caused by Scopulariopsis brevicaulis: report of two cases. Ann Dermatol. 2012 May24(2):209-13. Epub 2012 Apr 26.
Westerberg DP, Voyack MJ; Onychomycosis: Current trends in diagnosis and treatment. Am Fam Physician. 2013 Dec 188(11):762-70.
Tracey C et al; How to Treat Dystrophic Nails, Podiatry Today, 2013
Fungal Skin and Nail Infections: Diagnosis and Laboratory Investigation - Quick Reference Guide for Primary Care; GOV.UK, 2017
British Association of Dermatologists’ guidelines for the management of onychomycosis 2014; British Association of Dermatologists
Fungal nail infection; NICE CKS, March 2018 (UK access only)
Gupta AK, Simpson FC; New therapeutic options for onychomycosis. Expert Opin Pharmacother. 2012 Jun13(8):1131-42. Epub 2012 Apr 25.
British National Formulary (BNF); NICE Evidence Services (UK access only)
Nair AB, Al-Dhubiab BE, Shah J, et al; Constant Voltage Iontophoresis Technique to Deliver Terbinafine via Transungual Delivery System: Formulation Optimization Using Box-Behnken Design and In Vitro Evaluation. Pharmaceutics. 2021 Oct 1513(10). pii: pharmaceutics13101692. doi: 10.3390/pharmaceutics13101692.
Brown SJ; Efficacy of fluconazole for the treatment of onychomycosis. Ann Pharmacother. 2009 Oct43(10):1684-91. doi: 10.1345/aph.1M165. Epub 2009 Sep 23.
olde Hartman TC, van Rijswijk E; Fungal nail infection. BMJ. 2008 Jul 10337:a429. doi: 10.1136/bmj.39357.558183.94.
Chang CH, Young-Xu Y, Kurth T, et al; The safety of oral antifungal treatments for superficial dermatophytosis and onychomycosis: a meta-analysis. Am J Med. 2007 Sep120(9):791-8.
Foley K, Gupta AK, Versteeg S, et al; Topical and device-based treatments for fungal infections of the toenails. Cochrane Database Syst Rev. 2020 Jan 161:CD012093. doi: 10.1002/14651858.CD012093.pub2.
Scher RK, Tavakkol A, Sigurgeirsson B, et al; Onychomycosis: diagnosis and definition of cure. J Am Acad Dermatol. 2007 Jun56(6):939-44. Epub 2007 Feb 16.
Arroll B, Oakley A; Preventing long term relapsing tinea unguium with topical anti-fungal cream: a case report. Cases J. 2009 Jan 212(1):70. doi: 10.1186/1757-1626-2-70.