What is Onychomycosis?

Tricia Christensen
Tricia Christensen

Onychomycosis refers to fungal infections present in fingernails or toenails. It can be called nail ringworm and more commonly affects the toes. The condition causes the nail to take on a yellow color and the nail may look like it is opaque instead of clear. Onychomycosis additionally may damage the integrity of affected nails and they may break or crumble easily. Usually, this fungal infection doesn’t cause nail pain, but it does look painful and it’s pretty easy to notice. In very severe cases, nails may be painful.

Onychomycosis is a fungal infections in the fingernails or toenails.
Onychomycosis is a fungal infections in the fingernails or toenails.

There are many fungi present in a lot of human environments that can result in onychomycosis. It’s not always clear why some people develop reactions to these fungi while others don’t, especially when exposure is the same. One factor that may particularly encourage growth of these special fungi that attack the nails, called dermatophytes, is a warm and wet environment. If you have constantly sweaty feet and wear heavy shoes, you might encourage growth of dermatophytes, to the point where they create onychomycosis.

Wearing moisture wicking socks may help prevent nail fungus.
Wearing moisture wicking socks may help prevent nail fungus.

Treatment for this condition can be challenging, but usually involves taking oral antifungal medications that are prescribed by your physician. You usually have to take these meds for an extended period of time, about six to twelve weeks, and at first affected nails may not look completely cured. In fact, until new nail growth occurs and a fully new nail is in place, there may still be crumbling, yellowed or cloudy nails. It can help to trim the nails short, but not too short, so there is less discoloration showing.

Individuals with diabetes may experience poor circulation in the feet, which may cause them to be more susceptible to foot infections.
Individuals with diabetes may experience poor circulation in the feet, which may cause them to be more susceptible to foot infections.

If you suspect you have onychomycosis, you shouldn’t delay seeing a doctor. This condition isn’t like other fungal infections that can usually be treated with over the counter anti-fungal ointments. Unless contraindicated, prescription antifungal medications are the best method for treatment and most likely to result in cure.

Walking barefoot in public places may cause toenail fungus.
Walking barefoot in public places may cause toenail fungus.

It is especially important to see a doctor right away if you have diabetes and notice onychomycosis on the feet. Diabetics have to be particularly vigilant about foot care and are at much more risk for devastating feet infections. If you seem prone to developing fungal infections on feet, it can help to use moisture wicking socks, to keep the nails trimmed and clean, and to make sure to dry between the fingers and toes after baths and showers. In particular, make sure your feet are fully dry before putting on socks and shoes.

Diabetics should inspect all parts of the legs and feet for sores or wounds on a regular basis.
Diabetics should inspect all parts of the legs and feet for sores or wounds on a regular basis.
Tricia Christensen
Tricia Christensen

Tricia has a Literature degree from Sonoma State University and has been a frequent wiseGEEK contributor for many years. She is especially passionate about reading and writing, although her other interests include medicine, art, film, history, politics, ethics, and religion. Tricia lives in Northern California and is currently working on her first novel.

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Discussion Comments


I had this problem with two of my fingernails and kept trying to cover it up with nail polish.

In addition to this I tried several over the counter medications to try and get this cleared up. Nothing I tried would work, and I was embarrassed to be seen without nail polish on.

Once when I was at the doctor for something else, I showed him my fingernails. He said it was the nail fungus onychomycosis and started me on a prescription medication.

This was a slow process, but eventually my fingernails grew back in and looked normal. I still don't know what caused this problem, but know if it comes back again I won't wait so long to go to the doctor.


@orangey03 - I have the same thing happen to me every year. Once it is warm enough outside to wear sandals, I begin putting polish on my toenails.

By the end of the summer, they look really disgusting and yellow. Once I give them a break through the winter, my toenails look nice and white again.

Since this same cycle has repeated itself every year, I don't think it has anything to do with toenail onychomycosis.

I don't want to give up painting my toenails, so this year I am going to make sure and but a base coat underneath the polish to see if that keep my toenails from getting so discolored.


My husband works in construction, and he has to wear protective boots and socks all year round. In the summer, his feet sweat profusely.

This trapped moisture, combined with the fact that he forgets to trim his nails, led to chronic onychomycosis. After getting some medical help for it, he learned that he would have to make a few other changes in order to prevent the condition from returning.

Since giving up his career wasn't an option, he had to start wearing moisture-wicking socks. These helped keep his feet drier than before.

He also started trimming his toenails every two weeks. He keeps them nice and short now that he knows what having them long can cause.


I have a friend who likes to keep her toenails long enough to do french manicures on them. This means she has to have a couple of centimeters of nail protruding from the top of her toe in order to paint the tips white.

Last year, she got onychomycosis. It made her nails look so awful that she could no longer paint them that sheer pink color, because the grossness would show through.

She was tempted to just cover them up with colored polish, but she felt that some type of infection must have caused them to suddenly look so ugly, so she visited a doctor. The treatment he gave her was some sort of medicated clear polish, so in a sense, she did get to polish her nails.

However, the ugliness still showed, so she started wearing sandals that covered her toes. She did not wear flip-flops that whole summer.


@orangey03 – It is probably not a fungal infection. Onychomycosis has to be treated with medication. If your yellow nails are growing out on their own, then you most likely have just stained them by constantly wearing nail polish.

My mother had onychomycosis, and she had to take medicine for a long time. She waited and waited, and after about seven months, she could see that no healthy new nail had grown in, so she knew it had to be an infection.

Reluctantly, she went to her doctor. After several weeks of using the medication, she started to see some new growth of a normal color. She had to grow out the rest of her funky old nail, but at least a healthy one was replacing it.


I wonder if I might have onychomycosis. I keep nail polish on my toenails for about six months out of the year, so I assumed the yellow coloring was just due to staining. However, they do look particularly unhealthy, as though parts of them could fall off.

In late October, I remove my toenail polish for the winter. I do this so my nails can breathe, and because it saves time. I don't see any reason to spend thirty minutes polishing my toenails in winter, because no one will see them.

The yellow, unhealthy nail usually grows out by February or March, but by then, it is almost time to start painting them again. Could this be onychomycosis, or is it just polish staining?

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