Nail Fungus: Causes, Symptoms, Treatment, Is it Contagious?

About 10 percent of people in western countries must contend with nail fungus infections. Officially called onychomycosis, nail fungus is caused by fungi invading the nail plate, bed, or root. It makes the nail turn colors (usually brown or black), thicken, and sometimes smell badly. The fungus often causes debris to build up under the nail, making it difficult to cut which, in turn, may negatively impact your ability to wear shoes and walk comfortably.




The infection invades slowly. By the time you realize you have nail fungus, it’s usually too late to fix the problem quickly. Additionally, it can spread to other nails and may cause secondary yeast or bacterial infections. While toenails are affected the most by this disease, it can invade fingernails as well. Oftentimes, nail fungus is mistaken for other conditions such as senile nails or hematomas.

Causes and Risk Factors

Mild Nail FungusAlthough nail fungus is caused by a fungus, there are certain risk factors that increase your chances of getting an infection in your toenails or fingernails. For people who don’t have any underlying diseases, nail fungus commonly develops after they come in contact with the organism. The fungi that cause this nail disease love to live in moist, warm areas like showers and pools. So you are more likely to get the infection if you walk around barefoot in these areas.

Nail fungus is also more common in people who have athlete’s foot. Called tinea pedis, this foot disease is also caused by a fungus that makes the skin itchy, scaly, dry, and flaky. If the toenail is damaged, the fungi from athlete’s foot will settle into the injury and grow out of control.

Athletes and people who wear tight shoes that don’t allow for adequate circulation are also more apt to get nail fungus infections because of the constant trauma to the toenail and the increased likelihood of the feet sweating. This is particularly true if the shoes are worn for long periods of time.

Age also plays a part in whether or not a person will get a nail fungus infection as about 20 percent of people over the age of 55 struggles with this condition. This may be because of reduced immune function, especially if the person is suffering from a disease such as diabetes, psoriasis, cancer, AIDS, or any condition that suppresses the immune system.

If your hands are submerged in water for long periods of time (e.g. you’re employed as a dishwasher), you have a higher risk of getting the fungal infection because of the damage the water can do to the nail base and cuticles. This damage can provide the fungi with an opening to infect the nail.

Other activities or conditions that can cause nail fungus include:

  • Wearing artificial nails (the process of putting on the name requires damaging the nail surface)
  • Biting the nails
  • Living in humid and warm areas
  • Nail trauma
  • Smoking
  • Touching infected areas and not washing your hands afterwards
  • Taking immunosuppresent medications such as corticosteroids
  • Contact with the candida yeast, which causes vaginal thrush

In rare cases, the source of the infection is unknown.

Symptoms: What Does Nail Fungus Looks Like?Signs of Nail Fungus

Though there are several different types of fungus that can infect the nail, the most common culprit is Trichophyton rubrum. This organism, also known as a dermatophyte, is responsible for skin infections such as jock itch in addition to nail infections.




The nail infection starts off innocuously enough. The fungus usually appears in one spot on nail and then slowly spreads to cover the entire area. Over time, the nail may become brittle, break off, discolor (turn yellow, brown, or black), develop white or yellow patches, crack, or fill with debris.

Typically, there is no pain in the beginning. However, as the infection spreads, it may cause inflammation in the surrounding skin tissues. As noted previously, the nail may become too thick to cut and press uncomfortably against shoes, making it difficult or painful to walk.

The infection may manifest in the nail in one of three ways:

  • Distal Subungal Onychomycosis – In about 90 percent of cases, the fungus will begin growing in a corner of the toenail and advance inwards towards the cuticle. While it’s progressing, the nail may become thick, flaky and lift up, and you may develop athlete’s foot. This type of nail fungus is most common in people who swim frequently, have diabetes, are older, are immunosuppressed, or live with people that also have nail fungus infections.
  • Proximal Subungal Onychomycosis – Only about 3 percent of nail fungus cases develop in this manner. The fungus begins at the cuticle and spreads upwards to the rest of the nail. This type is most common in people with poor or damaged immune systems. However, it can occur whenever the cuticle or nail root is injured.
  • Candida – This type of nail fungus is actually caused by a yeast and may begin anywhere in the nail. While you can get this type of infection in the toenail, it is more common in fingernails. As the infection progresses, the nail turns yellow, white, or brown and becomes very thick. People who have this infection may also suffer from chronic paronychia or have oral yeast infections.

Symptoms Mistaken for Nail Fungus

Sometimes nails will develop symptoms that appear to be associated with nail fungus but actually are caused by other conditions or diseases.

  • Lines and ridges – It is normal for nails to develop lines or ridges in the nail plate. In particular, if you bite your nails, you may develop a large groove in the center. The condition may worsen in women during pregnancy.
  • Red or black nails – This indicates there is blood underneath the nail due to a hematoma. This condition is caused by serious trauma to the nail such as slamming the tip of your finger in a doorway. However, if you haven’t damaged your nail, you should have the spot inspected by a dermatologist to determine if it is melanoma.
  • Senile nails – The nails become more brittle, develop ridges, and the layers of nail will begin to separate as you age. This is normal, but is preventable by reducing the amount of time your nails soak in water. For example, wear gloves when you wash dishes.
  • Pitted nails – This may be caused by an underlying disease that negatively impacts the nail matrix, which is the place from which nails grow. It’s common in people who have psoriasis or other similar skin problems.
  • Green-colored nails – This may be caused by the invasion of the Pseudomonas bacteria, which typically occurs when the nail separates partially from the nail bed. The best way to handle this type of growth is to cut the nails as short as possible every month until it grows out. Avoid leaving bare hands in water for long periods of time, and be certain to completely dry the nail after taking a bath. If the infection is particularly bad, talk to a doctor about getting a prescription medication that may help treat it.
  • Paronychia – This is swelling and redness that develops on the skin around the nail. If the condition comes on suddenly, it’s typically caused by a bacterial infection in the cuticle. However, if it develops over time into a chronic condition, it’s generally caused by inflammation in the cuticle. Occasionally, yeast will opportunistically infect the inflamed cuticle at the same time, though. Keeping the nail dry and away from water as much as possible can aid in the healing process. If the infection is particularly bad, a doctor may prescribe hydrocortisone or similar steroid cream to reduce inflammation.
  • Repetitive trauma, such as that associated with participation in sports, can cause the nails to develop bruises and discoloration that looks like nail fungus. However, these injuries typically go away once the activity stops.

Treatment Options

Because of how slow nails grow, treating nail fungus tends to be a long, and sometimes expensive, process. While there are a variety of at home treatments—such as over-the-counter topical creams and ointments—that may be helpful, your doctor may prescribe oral medications such as Sporanox (itraconazole), Lamisil (terbinafine), or Diflucan (fluconazole). These medications can take four months or more to completely eliminate the infection and replace the discolored nail with healthy new nail.

Topical prescription medications include antifungal lacquer such as Penlac (ciclopirox), which is brushed directly onto the nail and other creams. Alternative remedies include tea tree oil and grapefruit seed extract. However, these may not be as effective as oral medicines.

In some cases, the doctor may completely remove the nail, especially if the infection is not responding to any other treatment.

When to Visit a Doctor

If you nails become deformed, discolored, or thickens substantially, it’s a good idea to make an appointment with a podiatrist or general practitioner. It can take a long time for a nail fungus infection to go away. The sooner you start treatment, the sooner you can get rid of the fungus.



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