# Fungal nail infection > A fungal nail infection (onychomycosis) can turn a nail discoloured, thick and crumbly. Other nail problems look similar, so a laboratory test of a nail sample confirms it. Treatment takes months and doesn't always work, so treating athlete's foot early and keeping shoes clean matter. Guide in [Skin and nails](https://footanklelowerlimb.com.au/learn/topics/skin-and-nails), from Foot Ankle Lower Limb: https://footanklelowerlimb.com.au/learn/fungal-nail-infection Reviewed by Andrew Schox, BSc(Hons) PGradDipPod MPod (Podiatrist) on 27 October 2026. Next review by 27 October 2027. - **It's common:** A fungal nail infection can turn a nail yellow, white or brown, thick and crumbly. - **Confirm it first:** Other nail problems look similar, so a nail sample should confirm fungus before tablets are started. - **It's slow to treat:** Treatment takes months, doesn't always work, and the nail may not look fully normal. - **Look after your skin too:** Treating athlete's foot early and keeping shoes and socks clean helps prevent it. - **Dark streaks need a check:** A dark stripe down a nail should be seen by your GP soon. ## What is a fungal nail infection? A fungal nail infection (onychomycosis) is an infection of the nail caused by fungi. It's the most common nail problem, making up about half of all nail disease [1]. It typically causes discolouration, thickening and lifting of the nail, and the skin around it can be affected too [2]. How many people have it depends on the country, age and type of fungus. In studies of the general population in Europe and North America, about 4% of people had it [3]. Hospital studies give higher figures, but these probably overstate how common it is [3]. ## What causes it, and who gets it? Most fungal nail infections are caused by dermatophytes (a group of fungi), mainly one called Trichophyton rubrum [4]. These are largely the same fungi that cause athlete's foot. They can live harmlessly on skin, but multiply in warm, moist, dark places such as inside shoes [5]. Athlete's foot can spread to the toenails if it isn't treated early [6]. The infection can also pass between people who live together: it's been seen in almost half of households with someone affected [7]. If someone at home has a fungal nail or skin infection, keep an eye on your own feet and nails. People with diabetes or a weakened immune system are at higher risk [8]. Complications are more common with poor circulation (peripheral vascular disease) or a weakened immune system, and in people with diabetes they can threaten the limb [4]. ## What does it look like, and how is it diagnosed? Early on there may be no symptoms. Later the nail can turn white, yellow, orange, brown or black, thicken, crumble or lift, and it may be uncomfortable in shoes [5]. Skin conditions such as psoriasis and lichen planus, or an injury to the nail, can look just like fungus [7], so how a nail looks isn't enough to go on. The diagnosis should be confirmed by testing a nail sample in a laboratory [4]. No test is perfect, and a negative result doesn't always rule out infection, so a repeat sample may be needed if the suspicion stays high [4]. ## What helps first? If you have athlete's foot, treating it early is a good first step, because it can spread to the nails [6]. Treatment for the nail itself is usually advised when the nail is uncomfortable, when how it looks upsets you, or when you have diabetes, vascular disease or a connective tissue disorder, because of a higher risk of skin infection (cellulitis) [6]. A podiatrist or GP can take a nail clipping for testing. Antifungal tablets shouldn't be prescribed until a laboratory test has confirmed the infection [9]. Because tablets can affect the liver, you'll need blood tests before and during treatment [5]. Tell your GP or pharmacist about any health conditions, allergies, other medicines, and pregnancy or breastfeeding, as many antifungals aren't suitable [10]. It isn't clear yet which first treatment works best, so talk through the options with your GP. ## What if that isn't enough? If a nail hasn't improved, ask your GP or podiatrist to check that the diagnosis was confirmed by a laboratory test [9]. It isn't clear yet which treatment works best once the first one has failed, so this is a conversation to have with your GP. Referral to a dermatologist (a skin doctor) is recommended if the infection isn't responding, the diagnosis is uncertain, or a growth under the nail is suspected [9]. It's also recommended if the infection has spread to other nails, is severe, has reached the nail matrix (where the nail grows from), or you have diabetes or psoriasis [7]. ## How long does it take, and how can I stop it coming back? Antifungal tablets are taken for at least three months, sometimes 9–12 months [5]. They don't always work, and the nail may never return fully to normal [5]. To help stop it coming back, look beyond the nail, because infections enter through the skin [11]. Treat athlete's foot early [6]. Cleaning shoes, socks, stockings and other textiles is described as an important part of preventing the infection returning and spreading [11]. > [!tip] Try this > Check between your toes for itchy, flaky or peeling skin, and treat it early; a pharmacist can advise. Wash or replace socks and shoes that may be contaminated, and think about other places your feet spend time, such as shared showers. ## When to see a podiatrist See your GP soon if: - a nail changes in colour, texture, shape or thickness and you don't know why [12]; - a dark stripe runs down a nail, especially if it widens, darkens or spreads to the skin around it. Don't wait to see whether antifungal treatment works [12][13]; - bleeding keeps coming from the same spot under a nail [13]. A dark band in a child's nail is very unlikely to turn cancerous, but it's still worth having it checked [14]. See a podiatrist or your GP if a nail is uncomfortable, spreads to other nails, or isn't improving with treatment. If you have diabetes, poor circulation or a weakened immune system, have nail changes checked early rather than waiting [4][6]. See your GP or a podiatrist the same day if: - the skin around the nail is painful, red, hot, swollen or oozing pus, or your foot is quickly getting more painful or red, or you feel unwell [5][12]; - you have diabetes and notice a wound, sore, blister or colour change on your foot; - you're taking antifungal tablets and your skin or the whites of your eyes turn yellow, you have pale stools and dark urine, your face, neck or tongue swell, or you get a severe skin reaction with peeling or blistering [10]. For urgent advice when it isn't an emergency, call healthdirect on 1800 022 222 (24 hours a day), or go to a Medicare Urgent Care Clinic. Call 000 and ask for an ambulance if you have difficulty breathing after starting antifungal tablets [10]. ## Common questions ### Can fungal nail infection spread to other people or other nails? Yes. It can pass between people who share a home, and it can spread from one nail to others. If someone you live with has it, keep an eye on your own feet and nails. If more than one nail becomes affected, ask your GP or podiatrist to take another look. ### Is fungal nail infection more serious if I have diabetes? It can be. Complications are more common in people with diabetes, and they can threaten the limb. That's why it's best not to wait and see. A podiatrist can check your nails and feet, so book a check as soon as you notice a nail change. ## Further reading - [Fungal nail infection on Clindice](https://clindice.com/fungal-nail-infection) - [Fungal nail infection](https://www.nhs.uk/conditions/fungal-nail-infection/), NHS - [Mycotic Nails: What Is It, Symptoms, Causes & Treatment](https://my.clevelandclinic.org/health/diseases/21712-mycotic-nails), Cleveland Clinic - [Toenail infection](https://www.healthdirect.gov.au/conditions/parasite-and-fungal-infections/toenail-infection), healthdirect - [Athlete's foot and fungal nails - The Dudley Group NHS Foundation Trust](https://www.dgft.nhs.uk/pil/athletes-foot-and-fungal-nails/), NHS - [Fungal Nail Infection (Onychomycosis) guide :: Mersey Care NHS Foundation Trust](https://www.merseycare.nhs.uk/patient-leaflets/fungal-nail-infection-onychomycosis-guide), NHS ## Sources 1. Monotherapy for toenail onychomycosis: a systematic review and network meta-analysis · Gupta AK, Foley KA, Mays RR et al. · The British Journal of Dermatology · 2020. https://doi.org/10.1111/bjd.18155 2. Unveiling onychomycosis: Pathogenesis, diagnosis, and innovative treatment strategies · Shah AA, Mirza R, Sattar A et al. · Microbial Pathogenesis · 2025. https://doi.org/10.1016/j.micpath.2024.107111 3. The prevalence of onychomycosis in the global population: a literature study · Sigurgeirsson B, Baran R · Journal of the European Academy of Dermatology and Venereology · 2014. https://doi.org/10.1111/jdv.12323 4. Oral antifungal medication for toenail onychomycosis · Kreijkamp-Kaspers S, Hawke K, Guo L et al. · The Cochrane Database of Systematic Reviews · 2017. https://doi.org/10.1002/14651858.cd010031.pub2 5. Fungal Nail Infection (Onychomycosis) guide · Mersey Care NHS Foundation Trust. https://www.merseycare.nhs.uk/patient-leaflets/fungal-nail-infection-onychomycosis-guide 6. Fungal Nail Infection: Causes, Symptoms, and Treatment · NHS. https://best.barnsleyccg.nhs.uk/media/pzbbc30i/fungal_nail_infection_tinea_unguium-may-2023.pdf 7. Onychomycosis: Recommendations for Diagnosis, Assessment of Treatment Efficacy, and Specialist Referral. The CONSONANCE Consensus Project · Piraccini BM, Starace M, Rubin AI et al. · Dermatology and Therapy · 2022. https://doi.org/10.1007/s13555-022-00698-x 8. Nails - fingernail and toenail problems · Better Health Channel · 2010. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/nails-fingernail-and-toenail-problems 9. Fungal nail infections · NHS. https://www.rightdecisions.scot.nhs.uk/dermatology-pathways/fungal-nail-infections/ 10. Antifungal medicines · NHS. https://www.nhs.uk/medicines/antifungal-medicines/ 11. The March Against Onychomycosis: A Systematic Review of the Sanitization Methods for Shoes, Socks, and Textiles · Gupta AK, Simkovich AJ, Hall DC · Journal of the American Podiatric Medical Association · 2022. https://doi.org/10.7547/21-223 12. Nail abnormalities · nidirect · 2017. https://www.nidirect.gov.uk/conditions/nail-abnormalities 13. Differential diagnosis of pigmented nail lesions · Bertanha L, Noriega LF, Di Chiacchio NG et al. · Anais Brasileiros de Dermatologia · 2024. https://doi.org/10.1016/j.abd.2024.01.005 14. Melanoma-like features in pediatric longitudinal melanonychia: A systematic review and meta-analysis · Tsai SY, Hamilton CE, Mologousis MA et al. · Pediatric Dermatology · 2024. https://doi.org/10.1111/pde.15597 --- This page is general information, not a diagnosis or a treatment plan for you. For advice about your own feet or legs, see a podiatrist or your doctor. In an emergency, call 000.