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There are different classifications of nail fungus — depending on type of fungus and manifestation — which may have somewhat different signs and symptoms. In general, however, you may have a nail fungal infection — also called onychomycosis (on-i-ko-mi-KO-sis) — if one or more of your nails are:

• Thickened
• Brittle, crumbly or ragged
• Distorted in shape
• Dull, with no luster or shine
• A dark color, caused by debris building up under your nail

Infected nails also may separate from the nail bed, a condition called onycholysis. You may feel pain in your toes or fingertips and detect a slightly foul odor.

When to see a doctor
Once a nail fungal infection begins, it can persist indefinitely if not treated. See your doctor at the first sign of nail fungus, which is often a tiny white or yellow spot under the tip of your nail.

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Nail fungal infections are typically caused by a fungus that belongs to a group of fungi called dermatophytes. But yeasts and molds also can be responsible for nail fungal infections.

What are fungi?
Fungi are microscopic organisms that don't need sunlight to survive. Some fungi have beneficial uses, while others cause illness and infection.

All of these microscopic organisms:

• Live in warm, moist environments, including swimming pools and showers
• Can invade your skin through tiny visible or invisible cuts or through a small separation between your nail and nail bed
• Cause problems only if your nails are continually exposed to warmth and moisture — conditions perfect for the growth and spread of fungi

Toenails vs. fingernails
Nail fungus occurs more in toenails than in fingernails.

• Toenails often are confined in a dark, warm, moist environment inside your shoes — where fungi can thrive.
• Diminished blood circulation to the toes as compared with the fingers makes it harder for your body's immune system to detect and eliminate the infection.

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Aging is the most common risk factor for nail fungus for several reasons, including:

• Diminished blood circulation
• More years of exposure to fungi
• Nails may grow more slowly and thicken with age, making them more susceptible to infection

Nail fungus tends to affect men more often than it does women, particularly those with a family history of this infection.

Other factors that can increase your risk of developing nail fungus include:

• Perspiring heavily
• Working in a humid or moist environment
• Having the skin condition psoriasis
• Wearing socks and shoes that hinder ventilation and don't absorb perspiration
• Walking barefoot in damp public places, such as swimming pools, gyms and shower rooms
• Having athlete's foot (tinea pedis)
• Having a minor skin or nail injury, a damaged nail, or another infection
• Having diabetes, circulation problems or a weakened immune system

©1998-2013 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
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Nail fungus can be painful and may cause permanent damage to your nails. It also may lead to other serious infections that can spread beyond your feet if you have a suppressed immune system due to medication, diabetes or other conditions.

Fungal infections of the nail pose the most serious health risk for people with diabetes and for those with weakened immune systems, such as people with leukemia or AIDS or organ transplant recipients.

If you have diabetes, your blood circulation and the nerve supply to your feet can become impaired. You're also at greater risk for cellulitis, a potentially serious bacterial skin infection. Therefore, any relatively minor injury to your feet — including a nail fungal infection — can lead to a more serious complication, requiring timely medical care. See your doctor immediately if you suspect nail fungus.

©1998-2013 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
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You're likely to start by seeing your family doctor or a general practitioner. However, in some cases when you call to set up an appointment, you may be referred immediately to either a doctor who specializes in skin conditions (dermatologist) or one who specializes in foot conditions (podiatrist).

To make the most of your time with your doctor, it's good to prepare for your appointment.

What you can do

• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Write down key personal information, including any major stresses or recent life changes.
• Make a list of all medications, vitamins and supplements you're taking.
• Write down questions to ask your doctor.

For nail fungus, your questions might include:

• What is likely causing my symptoms or condition?
• Are there other possible causes for my symptoms or condition?
• What tests do I need?
• What is the best course of action?
• What are the alternatives to the primary approach you're suggesting?
• I have other health conditions. How can I best manage them together?
• Is there a generic alternative to the medicine you're prescribing?
• Are there brochures or other printed material that I can take home? Are there websites you recommend?

Don't hesitate to ask any other questions you have.

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Your doctor will likely examine your nails first. To test for fungi, your doctor may scrape some debris from under your nail for analysis.

The debris can be examined under a microscope or cultured in a lab to identify what's causing the infection. Other conditions, such as psoriasis, can mimic a fungal infection of the nail. Microorganisms, including yeast and bacteria, also can infect nails. Knowing the cause of your infection helps determine the best course of treatment.

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Nail fungus can be difficult to treat, and repeat infections are common. Over-the-counter antifungal nail creams and ointments are available, but they aren't very effective. If you have athlete's foot as well as nail fungus, you should treat the athlete's foot with topical medication and keep your feet clean and dry.

Oral medications
To treat nail fungus, your doctor may prescribe an oral antifungal medication. Studies have shown the most effective treatments to be terbinafine (Lamisil) and itraconazole (Sporanox).

Your doctor is likely to recommend oral medication if you:

• Have diabetes or other risk factors for cellulitis
• Have a history of cellulitis
• Are experiencing pain or discomfort from your nail infection

These medications help a new nail grow free of infection, slowly replacing the infected portion of your nail. You typically take these medications for six to 12 weeks, but you won't see the end result of treatment until the nail grows back completely. It may take four months or longer to eliminate an infection. Recurrent infections are possible, especially if you continue to expose your nails to warm, moist conditions.

Antifungal drugs may cause side effects ranging from skin rashes to liver damage. Doctors may not recommend them for people with liver disease or congestive heart failure or for those taking certain medications.

Other treatment options
Your doctor may also suggest these nail fungus treatments:

• Antifungal lacquer. If you have a mild to moderate infection of nail fungus, your doctor may prefer to prescribe an antifungal nail polish called ciclopirox (Penlac). You paint it on your infected nails and surrounding skin once a day. After seven days, you wipe the piled-on layers clean with alcohol and begin fresh applications. Daily use of Penlac for about one year has been shown to help clear up some nail fungal infections.
• Topical medications. Your doctor may also opt for other topical antifungal medications. You may be advised to use these creams with an over-the-counter lotion containing urea to help speed up absorption. Topical medications usually don't cure nail fungus, but they may be used with oral medications. Your doctor may file the surface of your nail (debridement) to lessen the amount of infected nail to treat and possibly make the topical medication more effective.
• Surgery. If your nail infection is severe or extremely painful, your doctor may suggest removing your nail. A new nail will usually grow in its place, though it will come in slowly and may take as long as a year to grow back completely. Sometimes surgery is used in combination with ciclopirox to treat the nail bed.

Treating nail fungus with a laser or photodynamic therapy — intense light irradiates the nail after it's been treated with an acid — may also be successful. However, this new treatment may not be available everywhere.

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Sometimes, because current treatments can take a long time to work and aren't always effective, people turn to home remedies. Two remedies purported to help nail fungus are vinegar and Vicks VapoRub.

• Vinegar. While there's no direct evidence that a vinegar soak can cure nail fungus, some studies have shown that it can inhibit the growth of certain bacteria. Experts suggest soaking your feet for 15 to 20 minutes in a mixture of 1 part vinegar to 2 parts warm water. Be sure to rinse well and pat your feet dry when you're done. You can soak your feet like this daily. But if your skin becomes irritated, try soaking only two to three times a week.
• Vicks VapoRub. As with vinegar, there have been no controlled clinical trials to assess the effectiveness of Vicks VapoRub on nail fungus, but there have been numerous anecdotal reports that it works. There's no consensus on how often to apply this product, so check with your doctor before using it on your nails.

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To help prevent nail fungus and reduce recurrent infections, practice good hand and foot hygiene.

• Keep your nails short, dry and clean. Trim nails straight across and file down thickened areas. Thoroughly dry your hands and feet, including between your toes, after bathing.
• Wear appropriate socks. Synthetic socks that wick away moisture may keep your feet dryer than do cotton or wool socks (you can also wear synthetic socks underneath other socks). Change them often, especially if your feet sweat excessively. Take your shoes off occasionally during the day and after exercise. Alternate closed-toe shoes with open-toe shoes.
• Use an antifungal spray or powder. Spray or sprinkle your feet and the insides of your shoes.
• Wear rubber gloves. This protects your hands from overexposure to water. Between uses, turn the rubber gloves inside out to dry.
• Don't trim or pick at the skin around your nails. This may give germs access to your skin and nails.
• Don't go barefoot in public places. Wear shoes around public pools, showers and locker rooms.
• Choose a reputable manicure and pedicure salon. Make sure the salon sterilizes its instruments. Better yet, bring your own.
• Give up nail polish and artificial nails. Although it may be tempting to hide nail fungal infections under a coat of pretty pink polish, this can trap unwanted moisture and worsen the infection.
• Wash your hands after touching an infected nail. Nail fungus can spread from nail to nail.

©1998-2013 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.