Nail fungus: symptoms, treatment and how long it takes

In short

• Nail fungus changes the nail: it can become thick, brittle, dull, crumbly and white or yellow, and may lift from the nail bed.
• Toenails are affected far more often than fingernails, and the infection often follows athlete's foot.
• Other nail problems look similar, so a provider may take a nail sample before treatment.
• The infection clears only as a healthy nail grows out, which can take up to a year, and it can come back after successful treatment.
• Treat athlete's foot promptly, and see a provider early if you have diabetes, poor circulation or a weakened immune system.

What nail fungus is

Fungi feed on dead tissue in hair, nails and the outer layer of skin. Nail infections often follow a fungal infection of the foot, are more common in toenails and are more common in older adults. The CDC counts them as one form of ringworm, the same family of fungi that causes athlete's foot.

Fungi thrive where it is warm and damp, so the NHS notes that infection is more likely when feet are constantly warm and damp, or when someone wears sneakers for long periods and has hot, sweaty feet.

What it looks like

• The nail becomes thicker than usual, brittle or crumbly at the edges.
• Color changes: white or yellow streaks or patches, often starting at the tip.
• A dull appearance and debris under the nail.
• The nail may loosen or lift from the nail bed, and the surrounding skin can become swollen and painful in some cases.

Nail injuries and other nail conditions can look the same, which is why a provider may confirm the diagnosis rather than guess.

Risk factors

• A fungal infection of the foot, such as athlete's foot.
• Diabetes, poor circulation or nerve damage.
• A weakened immune system, for example after an organ transplant or during chemotherapy.
• Nail injuries, moist skin and tight footwear that traps moisture.
• Family history and older age.
• Public showers or locker rooms without protective footwear, and sharing towels or nail tools.

Prevention and daily care

1. Treat athlete's foot earlyIt can spread to the nails.
2. Keep feet clean and dryChange socks daily and avoid shoes that make your feet hot and sweaty.
3. Wear flip-flops in public showersThat includes gyms, pools and locker rooms.
4. Keep nails short and cleanDo not share towels, shoes or nail clippers, and avoid sharing manicure or pedicure tools.
5. Wash your handsDo so after touching an infected nail or foot.

Avoid removing the cuticle, since that can lead to infection. The CDC also warns against using steroid creams on a rash that could be ringworm, so check with a provider before treating any itchy, scaly patch of skin on your feet. If you have a fungal infection on one foot, wash and dry your feet carefully and do not share socks or shoes with other family members until it is treated.

If you have diabetes

The CDC advises people with diabetes to look at both feet every day, wash and dry them thoroughly, never walk barefoot and trim toenails straight across. Tell your provider promptly about thickened, yellow toenails, athlete's foot, blisters, sores, ulcers or an infected corn or ingrown toenail. Do not try to remove corns or calluses yourself. Foot ulcers in people with diabetes can become infected and heal poorly, so getting care early matters.

When to see a doctor, and red flags

See your primary care provider, a dermatologist or a podiatrist if an infection is severe, has not responded to treatment or has spread to other nails. See a provider sooner if you have diabetes or a weakened immune system, or if a finger becomes painful, red or starts draining pus.

Call 911 or go to an emergency room if you have a painful, swollen foot with fever and spreading redness, or if you have diabetes and a foot wound is draining pus, turning dark or not healing.

How it is confirmed

A provider examines the nails, and may take scrapings or a small nail sample. These can be checked under a microscope to identify the fungus or sent to a lab for culture, which can take several weeks. Testing matters because other nail conditions look similar.

Treatment options in general terms

Treatment depends on how much of the nail is involved and on your health. Options include brush-on antifungal nail products, used regularly for many months and not suitable for everyone, antifungal tablets prescribed by a provider, which may need blood tests to check the liver and are not suitable for everyone, and in badly affected nails removal of the nail under local anesthetic. MedlinePlus notes that laser treatment is less effective than medicine.

Be realistic: the infection is considered cleared when healthy nail grows back from the base, which is slow, medicines clear the infection in about half of patients, and it can return. Always use these medicines as prescribed by a doctor, and ask about side effects and interactions before starting.

1. Is it definitely fungus, and do I need a nail test?
2. Which treatment suits my health and other medicines?
3. How long until I can expect to see healthy nail?
4. How do I lower the chance of it coming back?

Questions and answers

Sources

1. NHS — Fungal nail infection
2. MedlinePlus — Fungal nail infection
3. CDC — About Ringworm
4. CDC — Diabetes and Your Feet

Sources checked on 29 October 2026.