Symptoms of nail fungus include a nail or nails that are:

• Thickened
• Discolored
• Brittle, crumbly or ragged
• Misshapen
• Separated from the nail bed
• Smelly

Nail fungus can affect fingernails, but it's more common in toenails.

When to see a doctor

You may want to see a health care provider if self-care steps haven't helped and the nail becomes increasingly discolored, thickened or misshapen. Also talk with your health care provider if you have:

• Diabetes and think you're developing nail fungus
• Bleeding around the nails
• Swelling or pain around the nails
• Difficulty walking

Nail fungus is caused by various fungal organisms (fungi). The most common is a type called dermatophyte. Yeast, bacteria and molds also can cause nail infections. The discoloration from a bacterial infection tends to be green or black.

Fungal infection of the foot (athlete's foot) can spread to the nail, and a fungal infection of the nail can spread to the foot. You can also get the infection from contact with spaces where fungi can thrive, such as the floor tile in a gym shower or inside dark, sweaty, moist shoes.

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

• Older age
• Wearing shoes that make your feet sweat heavily
• Having had athlete's foot in the past
• Walking barefoot in damp public areas, such as swimming pools, gyms and shower rooms
• Having a minor skin or nail injury
• Having a skin condition that affects the nails, such as psoriasis
• Having diabetes, blood flow problems or a weakened immune system

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.

The following habits can help prevent nail fungus or reinfections and athlete's foot, which can lead to nail fungus:

• Keep your nails clean and dry. Wash your hands and feet regularly. Wash your hands after touching an infected nail. Dry well, apply an antifungal foot powder and moisturize your nails. Consider applying a nail hardener, which might help strengthen nails and cuticles.
• Keep your nails trimmed. Cut nails straight across, smooth the edges with a file and file down thickened areas. Disinfect your nail clippers after each use. Letting your nails grow long creates more places for the fungus to grow.
• Wear absorbent socks or change your socks throughout the day.
• Choose shoes made of materials that breathe.
• Discard old shoes or treat them with disinfectants or antifungal powders.
• Wear footwear in pool areas and locker rooms.
• Choose a nail salon that uses sterilized manicure tools for each customer. Or disinfect tools you use for home pedicures.
• Give up nail polish and artificial nails.
• If you have athlete's foot, treat it with an antifungal product.

Your health care provider will examine your nails and perhaps take some nail clippings or scrape debris from under your nail. These samples are sent to a lab to identify the cause of your symptoms.

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 treatment.

Treatment for toenail fungus isn't always needed. And sometimes self-care and nonprescription products clear up the infection. Talk with your health care provider if your condition doesn't improve. Treatment depends on the severity of your condition and the type of fungus causing it. It can take months to see results. And even if your nail condition improves, repeat infections are common.

Medications

Your health care provider may prescribe antifungal drugs that you take by mouth (orally) or apply to the nail.

• Oral antifungal drugs. These drugs are often the first choice. One option is itraconazole (Sporanox). These drugs help a new nail grow free of infection, slowly replacing the infected part.

  You typically take this type of drug daily for 6 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.

  Oral antifungal drugs may cause side effects such as rash and liver damage. Or they may interfere with other prescription drugs. You may need occasional blood tests to check on how you're doing with these types of drugs. Health care providers may not recommend oral antifungal drugs for people with liver disease or congestive heart failure or those taking certain medications.

• Medicated nail polish. Your health care provider 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 almost a year.

• Medicated nail cream. Your health care provider may prescribe an antifungal cream, such as efinaconazole (Jublia) and tavaborole (Kerydin). You rub this product 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 a nonprescription lotion containing urea. Or your health care provider may thin the surface of the nail (debride) with a file or other tool.

  Antifungal nail creams may cause side effects such as rash.

Surgery

Your health care provider might suggest temporary removal of the nail so that the antifungal drug can be applied directly to the infection under the nail.

The most effective but least used option is surgery to permanently remove the nail and its root.

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

• Try nonprescription antifungal nail creams and ointments. Several products are available, such as terbinafine (Lamisil). If you notice white markings on the surfaces of the nails, file them off, soak your nails in water, dry them, and apply the medicated cream or lotion. Even if this clears up your symptoms, it's common for the infection to come back.
• 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 with urea-containing creams. See a health care provider for foot care if you have a condition that causes poor blood flow to your feet.

You're likely to start by seeing your primary care provider. 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).

Here are some steps you can take to prepare for your appointment:

• 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 health care provider.

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?