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What Causes Toenail Fungus?

Jun 15, 2024
Toenail fungus, medically known as onychomycosis, is a common condition caused by various types of fungi, including yeasts and molds. But where do the fungi come from, and how can you avoid them? Learn more here.

The fungi that cause onychomycosis thrive in warm, moist environments, which makes toenails particularly susceptible. Experts estimate that about 10% of Americans younger than 60 have toenail fungus. By the time you turn 70, however, you’ve got a 50/50 chance of developing the yellowed, crumbling nails the fungus causes.

With offices in Dallas, Garland, and Richardson, Texas, our podiatrists at Metroplex Foot and Ankle, LLP, are experts at diagnosing and treating conditions that affect your feet and ankles. We can help eliminate onychomycosis and the embarrassment it can cause.

Here, we offer insight into the origins, risk factors, and prevention strategies of fungal nails.  

Toenail fungus basics

Yeast and other fungal organisms cause toenail fungus. However, most infections — about 90% — come from a type of mold (dermatophyte) prevalent in the environment. Dermatophytes need a specific protein (keratin) to grow, which happens to be the substance that makes your nails hard.

Dermatophytes collect and grow between your nails and the nailbed, usually entering their new home through tiny cuts, abrasions, or openings at the tip of the toe. Toenails are most often affected, but dermatophytes can also invade fingernails.  

Risk factors for fungal toenails

Several factors can contribute to the development of toenail fungus:


Walking barefoot in damp communal areas such as locker rooms, showers, and swimming pools increases your risk of contact with the dermatophytes that cause onychomycosis.


Wearing tight, non-breathable shoes creates a warm, moist environment where fungi thrive.


Trauma to the nail or surrounding skin can provide an entry point for fungi.


Poor foot hygiene or excessive moisture around the feet can create an ideal environment for dermatophytes.

Underlying medical conditions

Conditions like diabetes, a weakened immune system, or poor circulation can increase your vulnerability to a fungal infection. Athlete’s foot, another fungal infection that can spread to your nails, also increases your risk.

Podiatrist treatment options for toenail fungus

Our Metroplex Foot and Ankle, LLP, podiatrists develop personalized treatment strategies for fungal nails that may include:

Topical antifungal medications

These medicines are applied directly to the affected nails and are most effective for mild to moderate fungal infections.

Oral antifungals

Severe or persistent infections benefit from oral antifungal medicines. Commonly used drugs include terbinafine and itraconazole. These medications can help new, uninfected nail growth replace the infected nail over time.

Nail debridement

Removing diseased nail material with debridement reduces fungal load and can improve the efficacy of topical treatments.

Surgical removal

In severe cases, your podiatrist may recommend removing the infected nail. It takes 12-18 months for the nail to grow back, giving you ample time to clear the infection.

Preventing nail fungus

You can’t always prevent nail fungus, but there are steps you can take to reduce your risks. Generally, you should:

  • Maintain good foot hygiene by washing daily and drying thoroughly
  • Wear breathable socks and shoes
  • Change your socks regularly, especially after exercise
  • Avoid walking barefoot in communal areas
  • Trim your nails regularly, straight across, and with clean, sterilized clippers
  • Disinfect your shoes with antifungal sprays or powders
  • Avoid sharing shoes, socks, or nail care tools with others
  • Treat athlete’s foot and other foot infections promptly
  • Support immune system function through diet, exercise, and sleep
  • Manage chronic health conditions such as diabetes

We also recommend checking your feet regularly and seeking early treatment if you notice signs of nail fungus, such as yellow or white spots on the nails, or abnormal growth patterns. Our team is always here to help — call or click online to schedule a visit at Metroplex Foot and Ankle, LLP, today.