Nail Fungus
Nail fungus is a slow infection of the nail itself, usually a toenail. It makes the nail thick, yellow-brown, crumbly and lifted away from the skin underneath. It is treatable, but treatment is measured in months, because the damaged nail has to grow out before anything looks better.
Key facts
Nail Fungus at a glance.
Typical signs
Thick, yellow, crumbly nails
Common locations
Mainly toenails
Expected course
Slow clearing; recurrence possible
Treatment options
Nail treatments or antifungal pills
What is it?
Top things to know about Nail Fungus
- Several organisms can cause it. Dermatophytes, yeasts or molds can invade nail keratin.
- It is not always trivial. Thickened nails can be painful in shoes and affect mobility.
- Testing confirms it. Nail clippings help distinguish infection from trauma, psoriasis and other nail disease.
- Some changes are not fungus. A new dark band, bleeding or destructive change should be examined, not assumed fungal.
What it looks like
What Nail Fungus looks like
Nail fungus usually starts as a white or yellow spot at the tip or side of a nail and slowly spreads toward the cuticle. Over months, the nail can thicken, crumble at the edges and lift away from the nail bed. Debris often builds up under the nail, and some infected nails have a faint smell. Toenails are affected far more often than fingernails, and the big toe is the most common place to start.
Nail fungus is grouped by where the infection enters the nail. The type affects how deep the fungus sits and which treatments are likely to reach it.
Distal subungual onychomycosis
The most common type, starting at the tip.
White superficial onychomycosis
Chalky white patches on the nail surface.
Proximal subungual onychomycosis
Starts near the cuticle; rarer.
Candidal nail infection
Caused by yeast, usually on fingernails.
Where it shows up
Toenails are more commonly involved, but fingernails can also be affected. The map locates the digits rather than depicting nail changes.
Fingernails
Fingernail locations; the nail surfaces face away in this view.
Toenails
Marked toe tips locate the toenails.
On different skin tones
Nail Fungus on different skin tones
Nail fungus looks similar on all skin tones because the color change is in the nail itself. On brown and Black skin, dark lines or brown streaks in the nail are common and often harmless, but they can be mistaken for fungus. A new dark band in a single nail should be checked by a doctor, since it can rarely be a sign of melanoma.
What happens in Nail Fungus?
Fungi invade the keratin that makes up the nail, often entering near an edge or a small break. Damage and debris can make the nail discolored, thickened or separated from its bed.
- Fungi enter the nail: Infection often begins near an edge.
- Keratin becomes damaged: Fungal growth disrupts the nail structure.
- The nail thickens or lifts: Debris can collect beneath a discolored nail.
Causes and triggers
What causes Nail Fungus
Causes
Why it happens
Nail fungus is caused by fungi, usually the same ones behind athlete's foot. They get into the nail through small cracks or the skin around it, then grow slowly.
Some families are more prone to fungal nail infections, likely because of inherited differences in skin immunity.
Risk factors
Raise the odds
- Age over 60
- Diabetes
- Athlete's foot
- Poor circulation
- Weakened immunity
Triggers
Passes it on
- Untreated athlete's foot (Well established)
- Damp shoes and socks (Strong link)
- Barefoot in shared showers and pools (Strong link)
- Nail injury (Strong link)
When it usually starts
When it usually starts
Nail Fungus
Can occur at any age but becomes more common in older adults.
Daily care
Daily care for Nail Fungus
Keep feet dry and rotate shoes
Dry between the toes, let each pair dry.
Shoes in communal wet areas
Where people acquire it.
Cut nails straight across
Less trauma, fewer splits.
Judge by the new nail at the base
Look for a clear band growing from the nail base.
Oral itraconazole
The alternative, but it interacts with many medicines.
Prescription topical treatments
Months of painting, low cure rates.
Treat the athlete's foot too
This is what stops reinfection.
Avoid: Wearing the same shoes every day
They stay damp longer than you think.
Avoid: Damp socks and sweaty feet
Synthetic socks, wet trainers, feet never dried.
Avoid: Nail trauma
Knocks and short shoes lift the nail.
Avoid: Cutting or filing corners aggressively
Digging the sides creates splits.
Avoid: Covering it with nail polish
Traps moisture, hides the new nail.
Avoid: Sharing clippers and files
Fungus transfers on tools easily.
Avoid: Walking barefoot in communal wet areas
Where most people pick it up.
Avoid: Leaving athlete's foot untreated
The skin between your toes reseeds it.
Avoid: Stopping because nothing has changed
Tablets work before the nail looks better.
Avoid: Very thick nails left unthinned
Medicine cannot get through.
Treatments
Treatments for Nail Fungus
Urea 40% nail softener
A strong urea cream or patch softens a thick nail so more of it can be filed or cut away. It kills nothing on its own. Its job here is to reduce the amount of dense nail sitting between a painted-on treatment and the fungus, and to make an uncuttable nail manageable.
Terbinafine cream
This will not cure the nail, but it clears the athlete's foot on the skin that keeps reseeding it. Use it on the whole sole and between the toes, not just the itchy bit, and carry on for a week or two after the skin looks normal. Treating the skin is the single cheapest thing you can do to stop the nail coming back after a course of tablets.
Tea Tree Oil
It does have antifungal activity in the laboratory, and the small studies in nails have shown some improvement in appearance. None have shown reliable cure of an established nail infection. It also cannot get through a thick nail, and it can irritate the skin around it.
Jublia
Jublia. A solution painted on the nail once a day for about a year. It penetrates nail better than the older lacquers, and it suits mild infection, one or two nails, or people who cannot take tablets. Complete cure rates are still well below tablets, so it is a reasonable choice rather than the strongest one.
Kerydin
Kerydin. Another daily paint-on solution used for about a year, with a small molecule that gets through the nail plate. Results are similar to the other topicals: many nails look better, far fewer clear completely. It works best on thin nails with the infection limited to the tip.
Ciclopirox
Penlac. The oldest of the prescription nail paints, applied daily with the built-up layers removed weekly with alcohol. Complete cure rates are low, in single figures in the original studies. It is cheap and safe, and it is mostly used when tablets are not an option.
Terbinafine
The first choice for dermatophyte nail infection and the option with the best cure rate: usually 12 weeks for toenails and 6 for fingernails. It binds into the nail and keeps working there for months after the last tablet. A liver blood test is standard, taste changes are a known side effect, and nothing will look different while you are taking it.
Itraconazole
The main alternative, and the better option when a yeast or a mould is grown rather than a dermatophyte. It is often given as pulses, a week on and three weeks off. It interacts with a long list of common medicines and is avoided in some heart conditions, so your doctor needs everything you take, including anything bought over the counter.
Fluconazole
Taken once a week rather than daily, which suits people who struggle with a long daily course. Cure rates sit below terbinafine and it usually has to be continued until the nail has grown out, which can be a year. It also interacts with a number of other medicines.
Griseofulvin
The old antifungal tablet, now largely replaced for nails. It needs 12 to 18 months of daily treatment, it clears fewer nails than terbinafine, and relapse afterwards is common. It is still occasionally used in children or when the newer drugs cannot be taken.
Nail Debridement
Thinning and clipping the nail. Cutting the nail back and filing or drilling down the thickened part, usually by a podiatrist. It is painless and it does two things: it takes pressure off a sore toe, and it removes dense nail and any packed clump of fungus that medicine cannot get through. Done alongside tablets or a nail paint, it makes them work better; done alone, it does not treat the infection.
Nd:YAG Laser
Laser devices are cleared to temporarily increase the amount of clear nail, which is not the same thing as curing the infection. Studies are small, short and mostly measure appearance rather than clearance, and the fungus commonly returns. It is usually several sessions, paid for out of pocket, and it is a reasonable thing to consider only when tablets are genuinely not an option.
Nail Removal
Removing the nail. Taking off part or all of the nail, either surgically or with a strong urea paste. It is not a cure on its own, because the fungus is also in the nail bed and the new nail grows back into it. It is kept for a nail that is painful, hopelessly thick, or holding a dense clump of fungus, and it is done alongside tablets rather than instead of them.
Outlook
What to expect with Nail Fungus
Nail fungus does not clear on its own. Left alone it takes over more of the nail and, over years, more nails. Once treatment starts, nail growth sets the timeline, so watch the base.
- 1
Left untreated · Months to years
It starts as a painless white or yellow patch under the tip or side of one nail, often a big toe, and gets blamed on a bump or on polish. Over years it works back toward the cuticle, the nail thickens, chalky debris builds underneath, and the nail lifts off the bed. It becomes brittle, hard to cut and uncomfortable in shoes.
- 2
Weeks 1 to 12 of treatment · Taking the course
Tablets run about 6 weeks for fingernails and about 12 for toenails. The medicine binds into the nail and keeps working after the course ends. Seeing no change here is normal.
- 3
Months 3 to 6 of treatment · The first real sign
Clear, normal nail appears at the base and grows forward. That band at the cuticle is the real measure, not the old nail.
- 4
Months 9 to 18 · Growing out
The damaged nail is cut away as it advances toward the tip. A toenail replaces itself in roughly 12 to 18 months, a fingernail in about 4 to 6.
- 5
After clearing · The years that follow
Some nails never look normal again if the nail-forming tissue was scarred. Reinfection is common, which is why the feet and shoes matter as much as the nail.
Complications
Complications to know about
Cellulitis
A thickened, cracked nail and the split skin around it give bacteria a way into the leg. The result is a spreading area of hot, swollen, tender skin, usually with feeling unwell and a fever, and it needs antibiotics quickly. It matters most for people with diabetes, poor circulation in the legs or a weakened immune system, which is why fungal nails are treated more actively in those situations.
Spread to other nails and the skin
Left alone, one infected nail slowly seeds the others, and the same fungus keeps the skin of the sole and the gaps between the toes scaly and itchy. This is athlete's foot and nail fungus feeding each other. Treating the nail while ignoring the skin is the usual reason people end up doing the whole course twice.
Permanent nail damage
If the infection has been there for years, the tissue that makes the nail can be scarred by the time it clears. The nail then grows back ridged, short or misshapen even though the fungus is gone. It is not common, and it is a reason to treat sooner rather than later rather than a reason to expect it.
When to get help
When to get help
When to seek care
Confirm the diagnosis before long treatment courses. Seek care sooner for diabetes, poor circulation, painful swelling or infection around the nail.
Lookalikes
What else could it be?
Nail Psoriasis
Nail fungus often begins at one toenail’s tip. Nail psoriasis more often causes pitting across several nails. They can overlap, so nail testing helps distinguish them.
Melanoma
Nail melanoma may form a widening, uneven dark band, sometimes spreading onto nearby skin. This needs examination rather than assuming the discoloration is fungus.
Questions
Questions you might be asking.
How long before my nail looks normal?
Longer than almost anyone expects. The medicine protects new nail as it forms, and a toenail takes roughly 12 to 18 months to replace itself, a fingernail about 4 to 6. Progress is a widening band of clear nail at the cuticle, not the tip.
Do I really need tablets, or can I use something on the nail?
It depends how much nail is involved. Prescription topicals suit mild infection, one or two nails, or when tablets are not suitable, and they avoid blood tests. Cure rates are distinctly lower and they need daily use for close to a year. For thick nails, several nails, or infection at the cuticle, tablets are what work.
Are the tablets dangerous?
Most healthy adults tolerate them well and serious problems are uncommon. Terbinafine can affect the liver, so a blood test before or during the course is standard, and taste changes are common. Itraconazole interacts with a long list of medicines and is avoided in some heart conditions. Your doctor needs a full list of what else you take.
Can I still paint my nails?
While you are being tested, no - polish makes sampling harder and hides what is happening. During treatment it is not forbidden, but it hides the new nail you are meant to be watching, and gel removal damages the plate. Going bare is more useful.
Will it come back?
It can, and in a meaningful number of people it does. The strongest protection is not another course of tablets - it is treating the athlete's foot, keeping feet dry, rotating shoes, and wearing something in communal wet areas.
Can I give it to my family?
It spreads within a household more than between strangers - shared floors, towels, bath mats and clippers. Use your own clippers and file, keep a separate foot towel, and treat any athlete's foot in the house. Ordinary contact is very unlikely.
Sources
Sources and further reading
Related
Keep exploring.
Nail Psoriasis
Fluconazole
Terbinafine
Melanoma
Tea Tree Oil
Nd:YAG Laser
Nail Fungus vs Nail Psoriasis
Ingrown Toenail vs Nail Fungus
Nail Fungus vs Chronic Paronychia
Nail Fungus vs Green Nail Syndrome
Nail Fungus vs Nail Trauma
