Health
Under the nail
Video · American Academy of Dermatology
How to treat and prevent nail fungus: Dermatologist tips
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A discolored, thickened toenail is one of the most common things a foot doctor sees, and one of the most stubborn. Something like one adult in ten has one at any given time, and the share rises with age. It is also the subject of an enormous amount of confident advice, most of which fails for a reason that has nothing to do with the remedy and everything to do with where the problem is sitting.
This is the plain version. It is slower and less satisfying than the version circulating in videos, and it has the advantage of being what the trials found.
The nail is a roof, and the trouble is under it
A nail plate is not skin. It is a dense, layered sheet of keratin built to take a blow, and it does that job well. The fungus that discolors it is not sitting on that sheet where a brush could reach it. It is underneath, in the nail bed, in the warm space between the plate and the toe.
That single fact explains most of the disappointment. Anything painted, soaked or rubbed onto the top of a nail has to cross the roof to reach the thing it is aimed at, and keratin is very good at not letting substances through. It is the same property that protects the toe from a dropped can. It does not stop being useful just because it is now inconvenient.
Fungal colonies also form what researchers call a biofilm — a dense mat the organisms build around themselves. Biofilms are studied across medicine, from dental plaque to infected implants, and the consistent finding is that organisms inside one are markedly harder to treat than the same organisms floating free. How much harder depends heavily on the organism and the method, and figures quoted for one setting travel badly to another, so we are not going to put a multiplier on it. The direction is not in dispute; the number you may have heard is doing more work than the evidence supports.
What the trials measured
Researchers use a deliberately hard standard called complete cure: the lab evidence of fungus gone and the nail grown back looking normal. Not improvement, not "clearer" — both, at the end of a full treatment course. Against that standard, here is roughly where the main options landed in their trials:
| Treatment | Complete cure in trials |
|---|---|
| Terbinafine, taken by mouth on prescription | About 38 percent |
| Efinaconazole, a prescription solution applied to the nail | About 15 to 18 percent at one year |
| Ciclopirox, a prescription lacquer applied to the nail | About 6 to 9 percent |
| Vinegar soaks, mentholated chest rubs, tea tree oil and the rest | Not established; the trials are small, short or absent |
Two things are worth saying about that table before anyone draws the wrong conclusion from it.
The first is that the best number on it is 38 percent, and it belongs to a prescription medicine taken by mouth for three months. That is the ceiling, not the floor. Anyone promising better than that, from a bottle, without a doctor, is promising something the best-studied option in the field has never managed.
The second is that the low numbers on the topical rows are not a scandal and not a cover-up. They are a barrier problem, published openly by the companies that ran the trials and reproduced in independent reviews. The lacquer is not fraudulent. It is doing its best against a roof.
It grows out. It does not wash off.
Here is the part that gets left out of almost everything written on this subject, and it may be the most useful sentence in the article: a damaged nail is never repaired. It is replaced, slowly, from the base.
A toenail grows about a millimeter a month. A big toenail is somewhere between twelve and eighteen months of growth from base to tip. So even in the best case — the treatment works, the fungus is gone, everything has gone right — the discolored part is still there, still visible, and will keep being visible until it has grown all the way out and been cut off.
This is why so many people conclude that something "stopped working" around week six. Nothing stopped. The nail was never going to look different by week six, because nail does not work that way. A great deal of money changes hands in that gap between what a treatment can do and when a person expects to see it.
It is also why relapse is common. Depending on how a study defines it, somewhere in the region of a fifth to a quarter of people see it return. The usual advice is dull and does more than it sounds like: dry the feet properly including between the toes, don't share clippers, treat the shoes as well as the foot, and wear something on the feet in shared showers and changing rooms.
When it stops being a cosmetic matter
For most people this is a slow, ugly, harmless nuisance, and it is reasonable to decide it is not worth a prescription. That is a legitimate choice and doctors make it with patients regularly.
It is not the right choice for everybody, and there are a few situations where the sensible move is an appointment rather than a shelf. Skin that is cracked or broken around a nail is an opening, and cellulitis — a bacterial infection of the skin that can spread and sometimes needs treating urgently — gets in through openings like that. The people for whom this matters most are those living with diabetes, with poor circulation in the legs, or with an immune system suppressed by illness or medication, for whom foot care is already part of routine medical advice rather than a matter of appearance. Pain, spreading redness, warmth or swelling in a foot is worth a call the same week, not a remedy.
There is a second reason to have it looked at, and it is more ordinary than alarming: not every thickened, discolored nail is fungus. Psoriasis does it, so does an old injury, and so do several other things. Studies of nails sampled in clinic routinely find that a meaningful share of nails assumed to be fungal are not. A course of treatment aimed at the wrong thing is months of nothing happening, which is a shame when a clipping sent to a laboratory settles it.
On the medicines taken by mouth
The prescription tablets are the most effective option and they are not free of trade-offs, which is exactly why they are a conversation with a doctor rather than a purchase. Terbinafine interacts with a number of common medicines, and liver problems, though uncommon, are a recognized risk that guidance addresses directly. Whether the trade is worth making depends on the nail, the person, and what else they take — three things an article cannot know and a prescriber can.
Three questions worth asking of anything you watch
A great deal of confident material about nails is published every week, and some of it is very well made. The same three questions this journal applies to blood pressure claims sort most of it quickly.
Does it name a number and a source? Real findings come with a size — thirty-eight percent, one millimeter a month — and somewhere to check it. "Dramatic results" is not a size, and neither is a multiplier with no study attached to it.
Does it respect how slowly a nail grows? This is the quickest test there is on this particular subject. Any before-and-after that shows a clear nail in a few weeks is showing something other than a nail that grew. Twelve to eighteen months is the honest timescale, and material that hides that is hiding the main thing.
Is something being sold at the end? Not disqualifying on its own. But it should change how carefully you listen to the middle — particularly when the middle spends a long time explaining why the alternatives cannot work.
Including us
That last question is only worth asking if we are willing to answer it about ourselves. This journal keeps a small shelf of ordinary household things called The Cupboard. Nothing on it is a supplement, nothing on it is a treatment for anything, and no item on it appears anywhere in this article. Not one sentence here would change if we closed the shelf tomorrow.
What to take to the appointment
If it is worth an appointment, a few minutes of preparation makes the appointment worth more. Note roughly when the change in the nail started and whether it has moved to other toes. Bring the list of everything swallowed in a day, prescription and otherwise, because it is the list that decides whether the tablets are on the table at all. Say whether anything hurts, because pain moves this up the queue. And ask whether a clipping should go to the laboratory before treatment starts rather than after.
We wrote about how to prepare for a short appointment in a previous issue, and most of it applies here without modification.
Before you change anything
This article is general information, not medical advice, and it cannot know anything about you. Antifungal medicines taken by mouth interact with a number of common prescriptions, and foot problems carry different weight for people with diabetes or with poor circulation. Talk it through with the doctor or pharmacist who knows your history before you make a change — and never adjust a prescription on your own.