A toenail that turns yellow, thick or crumbly is easy to ignore. It usually doesn't hurt. But toenail fungus, known medically as onychomycosis, is a real infection, and it tends to stick around. Cleveland Clinic describes it as "a widespread fungal infection" that happens "when fungi get between your toenail and your toenail bed."1
It is very common. Cleveland Clinic reports that it affects about 1 in 10 people overall, and about 1 in 2 people older than 70.1 The American College of Foot and Ankle Surgeons (ACFAS) notes that it can affect people of all ages, though it "most commonly affects individuals who are older."5
This guide covers what toenail fungus looks like, what causes it, why it matters more if you have diabetes or poor circulation, how it's usually treated, and when to see a podiatrist.
What Does Toenail Fungus Look Like?
According to Cleveland Clinic, an infected toenail may:1
- Turn white, yellow or brown
- Look chalky or cloudy in spots
- Thicken and look misshapen
- Separate from the nail bed
- Crack or break
MedlinePlus adds crumbling edges, debris trapped under the nail, loss of shine, and white or yellow streaks on the side of the nail.2 ACFAS explains that the fungus often starts under the nail fold at the tip of the toe, then grows under the nail over time.5
Toenail fungus "usually isn't painful," Cleveland Clinic says.1
Not every discolored nail is fungus, though. The American Academy of Dermatology (AAD) notes that "another nail condition, such as nail psoriasis or a nail injury, sometimes looks like nail fungus."3 A provider may take a nail sample for lab testing to find out what's really going on.1,3
What Causes Toenail Fungus?
Most cases come from a type of fungus called a dermatophyte, which feeds on keratin, the protein that makes up your nails. Cleveland Clinic says dermatophytes are behind 90% of toenail fungal infections.1 The fungi get in through small cracks in the nail or the skin around it.4,6
Toenail fungus often begins as athlete's foot, a fungal skin infection, that spreads to the nail.2,4,5 If you've dealt with itchy, peeling skin between your toes, read our post on athlete's foot.
Fungus thrives in warm, moist places.5 The CDC lists using public showers or locker rooms without footwear, wearing tight shoes and socks, and heavy sweating as common risks.6
Who Is More Likely to Get It?
Common risk factors include:1,2,5
- Athlete's foot
- Diabetes
- Poor circulation
- Nerve damage
- Heavy sweating, or feet that stay damp for long periods
- An injury to the nail
- Psoriasis
- A weakened immune system
- Older age or a family history of the condition
Why Does It Matter More With Diabetes or Poor Circulation?
If you have diabetes or circulation problems, toenail fungus deserves more attention.
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) explains that diabetes can lower blood flow to the feet, and "not having enough blood flowing to your legs and feet can make it hard for a sore or an infection to heal."7 Diabetes can also damage nerves in the feet.7
Cleveland Clinic notes that toenail fungus can spread to the skin between the toes and to other nails, and that "in rare cases, toenail fungus can cause an infection called cellulitis."1 It recommends seeing a provider if you have toenail fungus along with diabetes, circulation problems or a weakened immune system.1
NIDDK advises people with diabetes to check their feet every day and to have a foot doctor trim their toenails if the nails are "thick or yellowed," or if they can't see, feel or reach their feet.7 Learn more about diabetic foot care at Big Sky Foot & Ankle.
How Is Toenail Fungus Treated?
A podiatrist can help you weigh the options for your situation. Common approaches include:
- Prescription pills. Oral antifungal medicines such as terbinafine or itraconazole are taken daily, often for months.1,3 MedlinePlus puts it at about 2 to 3 months for toenails.2 These medicines can affect the liver and interact with other drugs, so your provider may order blood tests first.1,3
- Prescription topical medicine. These are applied to the nail. AAD notes that one such medicine is usually used once a day for 48 weeks.3 Cleveland Clinic says topicals work best when paired with oral medicine.1
- Nail care procedures. Trimming, thinning or removing the infected nail can be part of treatment.2,3
- Laser treatment. This is an option, but Cleveland Clinic notes that cure rates are lower than with oral and topical medicines.1
What about drugstore remedies? MedlinePlus says "over-the-counter creams and ointments usually do not help treat this condition."2
How Long Does It Take, and Can It Come Back?
Be ready for a long process. Cleveland Clinic is blunt: "Treating toenail fungus takes a long time, and it doesn't always work. Even then, toenail fungus often returns."1
- Results take time to show. Even when treatment works, MedlinePlus says it "may take up to a year for a new clear nail to grow."2 AAD notes that on the big toe it may take a year or longer.4
- It doesn't work for everyone. MedlinePlus reports that medicines clear the fungus in about half of the people who try them.2
- It can return. AAD says nail fungus "can return after clearing," sometimes a year or more later.3 For people with diabetes or damaged arteries or veins, AAD says ongoing "maintenance therapy" can be especially helpful.3
Patience and good daily habits matter.
How Can I Prevent Toenail Fungus?
- Wear shower shoes or sandals in public pools, showers and locker rooms.1,4,6
- Keep feet dry. Dry them fully after a shower.1
- Choose shoes that fit and avoid tight shoes and socks.1,6
- Keep nails clean, short and dry.4 Trim them straight across, without rounding the edges.1
- Don't share nail tools, and clean your nail trimmer before using it.1,2
- Don't ignore athlete's foot, since it can spread to the nails.2,4
When Should I See a Podiatrist?
ACFAS notes that "a foot and ankle surgeon can diagnose the cause of toenail problems and can recommend treatments."5 Consider making an appointment if:
- A nail is changing color, thickening or crumbling, and you aren't sure why
- You have diabetes, poor circulation or a weakened immune system1
- Your nails are too thick to trim safely on your own7
- The problem keeps coming back after treatment
Call right away if you notice redness, pain or pus near the nail,1 or skin on your foot that becomes red, warm or painful.7 If a nail is curving into the skin, see our page on ingrown toenails.
The Bottom Line
Toenail fungus is common, especially as we age. It usually isn't painful, and drugstore creams usually don't help. Treatment often takes months, a clear nail can take a year to grow in, and the fungus can come back. If you have diabetes or poor circulation, don't wait. Have a podiatrist take a look, and watch closely for signs of infection.
If you're concerned about a toenail, request an appointment and our team will follow up within one business day. You can also find your nearest office on our locations page.
This article is for general education and isn't a substitute for medical advice. Talk with a podiatrist or your doctor about your own symptoms.
Sources
- Toenail Fungus (Onychomycosis/Tinea Unguium): Symptoms & Causes. Cleveland Clinic. my.clevelandclinic.org
- Fungal nail infection. MedlinePlus Medical Encyclopedia, U.S. National Library of Medicine. medlineplus.gov
- Nail fungus: Diagnosis and treatment. American Academy of Dermatology. www.aad.org
- Nail Fungus: FAQs. American Academy of Dermatology. www.aad.org
- Nail Fungus. American College of Foot and Ankle Surgeons (FootHealthFacts.org). www.foothealthfacts.org
- What Causes Ringworm and Fungal Nail Infections. CDC. www.cdc.gov
- Diabetes & Foot Problems. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). www.niddk.nih.gov
