Nail fungus is a common condition that begins as a white or yellow spot under the tip of your fingernail or toenail. As the fungal infection goes deeper, nail fungus may cause your nail to discolor, thicken and crumble at the edge. It can affect several nails but usually not all of them.

If your condition is mild and not bothering you, you may not need treatment. If your nail fungus is painful and has caused thickened nails, self-care steps and medications may help. But even if treatment is successful, nail fungus often comes back.

Nail fungus is also called onychomycosis (on-ih-koh-my-KOH-sis) and tinea unguium. When fungus infects the areas between your toes and the skin of your feet, it's called athlete's foot (tinea pedis).

You may have nail fungus — also called onychomycosis (on-ih-koh-my-KOH-sis) — if one or more of your nails are:

  • Thickened
  • Brittle, crumbly or ragged
  • Distorted in shape
  • Dull, with no 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 (on-ih-KOL-ih-sis). You may feel pain in your toes or fingertips and detect a slightly foul odor.

When to see a doctor

You may want to see a physician if self-care steps haven't helped. Also see a doctor if you have diabetes and think you're developing nail fungus.

Nail fungal infections are typically caused by a dermatophyte fungus. 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. Others cause illness and infection. Fungi:

  • Live in warm, moist environments, including swimming pools and showers
  • Can invade your skin through cuts so tiny you can't even see them or through a small separation between your nail and nail bed
  • Can cause problems if your nails are often exposed to warm and moist conditions

Toenails vs. fingernails

Nail fungus occurs more often in toenails than in fingernails, partly because:

  • Toenails often are confined in a dark, warm, moist environment — inside your shoes — where fungi can thrive
  • Toes usually have less blood flow than do fingers, making it harder for your body's immune system to detect and stop infection

Factors that can increase your risk of developing nail fungus include:

  • Being older, owing to reduced blood flow, more years of exposure to fungi and slower growing nails
  • Perspiring heavily
  • Being male, especially if you have a family history of nail fungal infections
  • Working in a humid or moist environment or in a job where your hands are often wet, such as bartending or housekeeping
  • Wearing socks and shoes that hinder ventilation and don't absorb perspiration
  • Living with someone who has nail fungus
  • Walking barefoot in damp communal areas, such as swimming pools, gyms and shower rooms
  • Having athlete's foot
  • Having a minor skin or nail injury or a skin condition, such as psoriasis
  • Having diabetes, circulation problems, a weakened immune system or, in children, Down syndrome

A severe case of nail fungus can be painful and may cause permanent damage to your nails. And it may lead to other serious infections that spread beyond your feet if you have a suppressed immune system due to medication, diabetes or other conditions.

If you have diabetes, you may have reduced blood circulation and nerve supply in your feet. You're also at greater risk of a bacterial skin infection (cellulitis). So any relatively minor injury to your feet — including a nail fungal infection — can lead to a more serious complication. See your doctor if you have diabetes and think you're developing nail fungus.

You're likely to start by seeing your family doctor or a general practitioner. 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

  • List your symptoms, including any that may seem unrelated to nail fungus.
  • List key personal information, including any major stresses or recent life changes.
  • List all the medications, vitamins and supplements you're taking.
  • List questions to ask your doctor.

For nail fungus, your questions might include:

  • What is likely causing my symptoms or condition?
  • What are 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 a generic alternative available for the medicine you're prescribing?
  • Do you have any brochures or other printed material that I can take home? Do you recommend any websites on nail fungus?

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

Your doctor will likely examine your nails first. He or she may scrape some debris from under your nail and send it to a lab to identify the type of fungus causing the infection.

Other conditions, such as psoriasis, can mimic a fungal infection of the nail. Microorganisms such as yeast and bacteria also can infect nails. Knowing the cause of your infection helps determine the best course of treatment.

If self-care strategies and over-the-counter (nonprescription) products haven't helped, your doctor may suggest a combination of prescription drugs and other approaches. But even if you find relief from your signs and symptoms, repeat infections are common.

Medications

  • Oral antifungal drugs. Your doctor may prescribe an oral antifungal drug. Studies show the most effective treatments are terbinafine (Lamisil) and itraconazole (Sporanox). These drugs help a new nail grow free of infection, slowly replacing the infected part.

    You typically take this type of drug 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.

    Treatment success rates with these drugs appear to be lower in adults over age 65. And treatment success seems to improve when you combine oral and topical antifungal therapies.

    Oral antifungal drugs may cause side effects ranging from skin rash to liver damage. You may need occasional blood tests to check on how you're doing with these types of drugs. Doctors may not recommend them for people with liver disease or congestive heart failure or those taking certain medications.

  • Medicated nail polish. Your doctor may 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. You may need to use this type of nail polish daily for a year.
  • Medicated nail cream. Your doctor may prescribe an antifungal cream, which you rub into your infected nails after soaking. These creams may work better if you first thin the nails. This helps the medication get through the hard nail surface to the underlying fungus.

    To thin nails, you apply an over-the-counter (nonprescription) lotion containing urea. Or your doctor may thin the surface of the nail (debride) with a file or other tool.

Surgical or other procedures

  • Nail removal. 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. But 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.
  • Laser and light-based therapies. More study is needed, but these methods — alone or with medications — may help your nails improve. One study tested the effectiveness of carbon-dioxide laser therapy combined with antifungal nail cream. Most of the 24 people in the study benefited from the treatment.

    Laser and light-based therapies are not available everywhere, are expensive, and often are not covered by insurance.

Often, you can take care of a fungal nail infection at home:

  • Try over-the-counter antifungal nail creams and ointments. Several products are available. If you notice white markings on the surface of the nail, file them off, soak your nails in water, dry them, and apply the medicated cream or lotion.

    If you have athlete's foot as well as nail fungus, treat the athlete's foot with medicated powders or sprays and keep your feet clean and dry.

  • Apply Vicks VapoRub. Many people have had success with Vicks VapoRub. One study of 18 patients showed that 56 percent had partial improvement of signs and symptoms, and 17 percent saw no improvement. To use this method, apply a small amount of the product daily with a cotton swab.
  • Trim and thin the nails. This helps reduce pain by reducing pressure on the nails. Also, if you do this before applying an antifungal, the drug can reach deeper layers of the nail.

    Before trimming or using a nail file to thin thick nails, soften them. You can do this with the following nightly routine: Apply urea cream to affected nails, cover them with a bandage, and wash off the urea with soap and water in the morning. Repeat until the nails soften. Protect the skin around your nails with petroleum jelly.

    If you have a condition that causes poor blood flow to your feet and you can't trim your nails, see a health care provider regularly to have your nails trimmed.

Some people have had success with alternative approaches to treating nail fungus:

  • Snakeroot extract. This product comes from plants of the sunflower family. In a study of 110 people, it was about as effective as ciclopirox. It was applied every third day for the first month, twice a week for the second month and once a month for the third month.
  • Tea tree oil. This product, applied twice a day, is possibly effective in treating nail fungus, but more study is needed.

These habits can help prevent nail fungus or reinfections:

  • Wash your hands and feet regularly and keep your nails short and dry. Wash your hands and feet with soap and water, rinse, and dry thoroughly, including between the toes. Trim nails straight across and file down thickened areas.
  • Wear socks that absorb sweat. Fabrics effective at wicking away moisture include wool, nylon and polypropylene. Change your socks often, especially if you have sweaty feet.
  • Choose shoes that reduce humidity. It also helps to occasionally take off your shoes or wear open-toe footwear.
  • Discard old shoes. If possible, avoid wearing old shoes, which can harbor fungi and cause a reinfection. Or treat them with disinfectants or antifungal powders.
  • 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 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 sandals or shoes around pools, showers, and locker rooms.
  • Choose a reputable nail salon. Make sure the place you go for a manicure or pedicure sterilizes its instruments. Better yet, bring your own and disinfect them after use.
  • 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.
Jul. 26, 2014