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What is a fungal nail infection?
A fungal nail infection occurs when a fungus attacks a fingernail, a toenail, or the skin under the nail, called the nail bed. Fungi (plural of fungus) can attack your nails through small cuts in the skin around your nail or through the opening between your nail and nail bed.
If you are healthy, a fungal nail infection probably won't cause serious problems. But it may look bad, hurt, or damage your nail or nail bed.
A fungal nail infection could lead to more serious problems if you have diabetes or a weak immune system. Talk to your doctor about the best way to treat a nail infection if you have one of these problems.
What causes a fungal nail infection?
Yeasts, moulds, and different kinds of fungi can cause fungal nail infections. Most are caused by the same type of fungus that causes athlete's foot.
Fungi grow best in warm, moist places, and they can spread from person to person. You can get a fungal nail infection from walking barefoot in public showers or pools or by sharing personal items, such as towels and nail clippers. If you have athlete's foot, the fungus can spread from your skin to your nails.
What are the symptoms?
A nail with a fungal infection may:
- Turn yellow or white.
- Get thicker.
- Crumble and split, and it may separate from the skin.
When you have a fungal nail infection, it can be uncomfortable or even painful to wear shoes, walk, or stand for a long time. The fungus could also spread to other nails or your skin. Over time, the infection can cause permanent damage to your nail or nail bed.
How is a fungal nail infection diagnosed?
Your doctor will diagnose a fungal nail infection by looking at the nail, asking about your symptoms and past health, and possibly doing tests to look for fungi.
How is it treated?
Whether to treat a fungal nail infection is up to you. If it isn't treated, it won't go away. It might get worse.
If you decide to treat a fungal nail infection, you can try a non-prescription antifungal medicine that comes in a cream, lotion, or nail polish. Your doctor can also prescribe a stronger medicine. You may need to use this medicine for a few weeks or for as long as a year. Even so, it may not get rid of the infection.
Antifungal pills give the best chance of curing a severe fungal nail infection. But they may cost a lot and have serious side effects. You will need to see your doctor for regular testing if you take these pills.
How can you prevent a fungal nail infection?
Fungal nail infections often come back after treatment. It is important to take steps to prevent this.
- Before bed, wash and dry your feet carefully.
- Wear sandals or roomy shoes made of materials that allow moisture to escape. Let shoes dry for 24 hours before you wear them again.
- Wear socks. Change them if your feet get sweaty.
- Do not share nail files or clippers, socks, towels, or other personal items.
- Wear flip-flops or shower sandals in wet public areas, such as locker rooms or showers.
Fungal nail infections can be caused by three different types of fungus, alone or in combination.
- Dermatophytes are a type of fungus that can grow on the skin, hair, and nails. They don't invade the deeper tissues of the body. The most common dermatophyte, Trichophyton rubrum, causes most cases of athlete's foot. Athlete's foot, in turn, can infect the toenails. You can get infected by contact with objects that have dermatophytes on them, such as clothing, shoes, nail clippers, nail files, shower and locker room floors, and carpet. Dermatophytes cause almost all fungal toenail infections.
- Yeasts are a type of fungus that grows on the skin and nails. They are normally present on the human body. Things like illness, antibiotic or birth control pill use, and immune system problems may allow an overgrowth of yeast, leading to a yeast infection.
- Moulds (often called non-dermatophytes) are a type of fungus that commonly grows in soil and can grow on the skin and nails. They aren't usually passed between people.
You can get a fungal nail infection when you come in contact with the fungus and it begins to grow on or under your nail. Fungi grow best in warm, moist areas, such as the area around the toes. But you can have fungi on your skin without getting a nail infection. You have to be likely to get the infection (susceptible) for it to develop. If you are susceptible to fungal infections, they tend to return, even after successful treatment and especially if you don't take preventive steps.
It is not clear why some people are more susceptible to fungal infections than other people.
A fungal nail infection usually isn't painful. But without treatment, over time it can become uncomfortable or even painful to wear shoes, walk, or stand for a long time.
Your symptoms will depend on the type of infection you have. The two most common infections are both caused by dermatophytes.
Distal subungual onychomycosis affects both the nail and the skin underneath the nail (nail bed). Symptoms include:
- Yellow streaks in the nail bed and on the underside of the nail.
- Buildup of bits and pieces of skin and nail fragments (debris) under the nail.
- A discoloured and thickened nail that may separate from the skin under the nail.
- A brittle, broken, and thickened nail.
White superficial onychomycosis is a fungal infection of the nail surface. Symptoms include:
- White spots or streaks on the nail surface.
- Soft and powdery nail surface, as the infection gets worse.
- Damaged, crumbly, and brown or grey nail surface. But the nail doesn't separate from the skin underneath.
Conditions with similar symptoms
Fungal infections are classified by where they begin and what they affect. Most fungal nail infections affect the skin under the nail (nail bed) and the nail itself (nail plate).
Fungal nail infections typically get worse, or progress, very slowly. The rate at which a fungal infection progresses depends on:
- Your overall health and susceptibility to the infection.
- The levels of humidity and heat in your environment.
- The type of nail infected. Fungal nail infections of the toenail have more time to grow and spread, because toenails grow more slowly than fingernails.
You may first notice a fungal nail infection when a nail or skin under the nail (nail bed) becomes discoloured, damaged, thickened, or broken. If not treated, a fungal infection is likely to get worse and spread to other parts of the nail, the nail bed, and possibly the surrounding skin. Over time, the whole nail may become infected and damaged and may eventually fall out.
Fungal nail infections can be treated successfully. But some types are easier to treat than others. The most common type, distal subungual onychomycosis, can be a lifelong infection and hard to treat. Another type, white superficial onychomycosis, is easy to treat. Even after treatment, your nails may still look irregular in shape and appearance. It can take a year or longer before they return to normal.
Fungal nail infections often return. Of people successfully treated with antifungal pills, 15% to 20% get another infection in the next year.footnote 1
Bacterial infection can be a complication of a fungal nail infection. A common bacterial infection, acute paronychia, causes inflammation and swelling of the skin and tissues near a fingernail or toenail.
What Increases Your Risk
You are more likely to get a nail infection if you:
- Are older than 60.
- Have diabetes or a weak immune system.
- Have a nail injury like a hangnail or an ingrown toenail.
- Wear shoes that make your feet moist or sweaty.
- Live or work in a hot, humid place
When should you call your doctor?
Call your doctor for an immediate appointment if a fungal nail infection shows signs of bacterial infection, such as:
- Increased pain, swelling, redness, tenderness, or heat.
- Red streaks extending from the area.
- Discharge of pus.
- Fever of 38°C (100.4°F) or higher with no other cause.
Call your doctor for an appointment if your symptoms are troubling you, such as when:
- A fungal infection appears to be spreading to the skin under the nail, the nail itself, or the surrounding skin.
- The infected area is painful.
- A thickened toenail causes discomfort.
- Your nail's appearance concerns you.
If you think you have a fungal nail infection, see your doctor. Your doctor can check your nail and recommend ways to treat it.
Watchful waiting is a wait-and-see approach. If you get better on your own, you won't need treatment. If you get worse, you and your doctor will decide what to do next. If a nail is discoloured or damaged but isn't painful, you may decide not to treat the infection. Antifungal medicine doesn't guarantee a cure, and antifungal pills (oral medicine) can be expensive and have potentially dangerous side effects. But treatment may stop the infection from causing permanent damage to the nail and increase the chance of a cure.
Who to see
Examinations and Tests
To determine the cause of a nail problem and diagnose a fungal nail infection, your doctor:
- Will ask about your medical history, including any previous symptoms of nail damage or fungal nail infections.
- Will look at the skin and nails on your hands and feet.
- May take a sample of the bits of skin and nail fragments (debris) from under the infected nail. If a sample of debris can't be taken easily, a nail sample may be taken by lightly scraping the nail near the infected area or by using a small blade to shave off a piece of nail.
Tests used to examine nail and debris samples include:
- KOH (potassium hydroxide) preparation. This test can find out if the nail or skin condition is caused by fungi. This test can be done in a clinic or doctor's office.
- A fungal culture. This can show which type of fungus is present. Fungi typically grow slowly, so it can take several weeks for a culture to produce test results.
Almost all fungal toenail infections are caused by a type of fungus called a dermatophyte. Because of this, if the KOH test shows that there's a fungus present, your doctor may assume that the infection is caused by a dermatophyte and prescribe treatment. But because one medicine may work better than another medicine against certain types of fungus, your doctor may want to do a fungal culture.
Your doctor may remove a small piece of nail and look at it under a microscope (nail biopsy) if the KOH preparation and fungal culture do not show the presence of fungi but a fungal infection is still suspected.
Whether to treat a fungal nail infection is up to you. For example, you may decide not to treat a fungal nail infection if your nail is discoloured or damaged but not painful.
Treatment for a fungal nail infection includes using medicines and possibly removing the affected nail.
Treatment often starts with antifungal medicines. A cream, gel, or nail polish may be used. You can buy some of these medicines yourself, but you'll need a prescription for others.
- Antifungal creams, gels, and nail polish may be used for mild-to-moderate infections and to help prevent an infection from returning. They may also prevent athlete's foot from spreading to the nails. These medicines may not work as well as oral medicines.
- Antifungal pills (oral medicine) are typically used for moderate-to-severe or hard-to-treat fungal nail infections. They offer the best chance of a cure.
- Removal of an infected nail is used for severe or recurring fungal nail infections. Nail removal is rarely needed. It can be done without surgery or with surgery.
Your doctor will prescribe a topical or oral antibiotic if you get a bacterial infection along with the fungal infection.
What to think about
Some people are not sure whether they want to use antifungal pills because of the side effects.
If you have a condition such as diabetes that might complicate a minor foot injury or infection, your doctor may suggest treating a fungal nail infection, even if it doesn't bother you.
Combining nail removal with antifungal creams or pills is likely to be more effective than using one of these treatments alone.
If you have a mild fungal infection or are concerned about the risks of oral antifungal medicine, consider using a topical treatment, such as Lamisil or Penlac.
Even after treatment, your nails may still look irregular in shape and appearance. It can take a year or longer before they return to normal.
Fungal nail infections often come back.
After your fungal nail infection has been successfully treated, take steps to prevent the infection from coming back.
- Before bed, thoroughly wash and dry your feet or hands. Then apply a topical antifungal, such as terbinafine (Lamisil) or ciclopirox (Penlac), directly to your skin or nail. Use the topical medicine twice a week for up to 1 year.footnote 2
- Keep your feet and hands dry. Dry skin and nails are less likely to become infected. Apply powder to your dry feet or hands after you take a shower or bath.
- Wear socks. If they get damp, change them to keep your feet dry.
- Wear sandals or dry roomy shoes made of materials that allow moisture to escape.
- Wear shower sandals or shower shoes when using a public pool or shower. Let them dry between uses.
- Don't share shoes, socks, nail clippers, or nail files with others.
- Avoid injuring your nail. Cutting nails too short is a common cause of nail injury. If you decide to get artificial nails or have a manicure, go to a salon that uses sterile instruments. Nail manicure and certain nail products can damage the nail or cuticle, making the nail more susceptible to infection.
If you have diabetes, take special care of your feet to prevent nail infections. And if you smoke, try quitting.
If you have a mild fungal nail infection or are concerned about the risks of taking antifungal pills, try an antifungal medicine you put directly on your skin (topical medicine).
Some people find that tea tree oil or cream works well for treating and preventing athlete's foot and mild fungal nail infections.footnote 3 Some people have found Vicks VapoRub to be useful for treating fungal nail infections.footnote 4
After an infection has cleared up, take steps to prevent it from coming back.
Antifungal medicine is standard treatment for a fungal nail infection. The goals of treatment are to have few or no side effects, provide a long-term cure, and reduce treatment time.
- Antifungal pills (oral medicine) offer the best chance of a cure. But they also require close monitoring for dangerous side effects. Oral medicines are typically reserved for moderate-to-severe or hard-to-treat fungal nail infections.
- Antifungal topical medicines (creams, lotions, gels, and lacquers) are applied to the infected nail and surrounding areas of the skin. But they may not be as effective as oral medicines. Topical medicines may be used for mild-to-moderate infections and to help prevent an infection from returning or to prevent athlete's foot from spreading to the nails.
What to think about
If you're thinking about using oral medicines, you may want to think about the type of infection you have, the cost of treatment, side effects, and how the pills can help or hurt you.
Surgical nail removal may be used to treat severe or recurring fungal nail infections. After the diseased nail tissue is removed, an antifungal cream can be applied directly to the infected area. This is likely to work better than using one of these treatments alone. Nail removal is rarely needed.
Non-surgical nail removal may be used to treat severe or recurring fungal nail infections. A urea ointment is applied to the nail. The ointment softens and dissolves the nail so that it can be easily removed. After the diseased nail tissue is removed, an antifungal cream can be applied directly to the infected area. This is likely to work better than using one of these treatments alone. Nail removal is rarely needed.
Laser treatments for fungal nail infections use a highly focused beam of light on the infected toenail. Some people may find it helpful. It may take several treatments and about 6 months for the infection to clear up. But there is no good proof yet that this treatment works.
- Habif TP, et al. (2011). Tinea of the nails (Onychomycosis). In Skin Disease: Diagnosis and Treatment, 3rd ed., pp. 259–262. Edinburgh: Saunders.
- Habif TP (2010). Fungal nail infections section of Nail diseases. In Clinical Dermatology: A Color Guide to Diagnosis and Therapy, 5th ed., pp. 956–961. Edinburgh: Mosby Elsevier.
- Murray MT, Pizzorno JE Jr (2006). Melaleuca alternifolia (tea tree). In JE Pizzorno Jr, MT Murray, eds., Textbook of Natural Medicine, 3rd ed., vol. 1, pp. 1053–1056. St. Louis: Churchill Livingstone Elsevier.
- Derby R, et al. (2011). Novel treatment of onychomycosis using over-the-counter mentholated ointment: A clinical case series. Journal of the American Board of Family Medicine, 24(1): 69–74.
Current as of:
July 2, 2020
Author: Healthwise Staff
Patrice Burgess MD - Family Medicine
Brian D. O'Brien MD - Internal Medicine
Adam Husney MD - Family Medicine
Martin J. Gabica MD - Family Medicine
E. Gregory Thompson MD - Internal Medicine
Ellen K. Roh MD - Dermatology
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