Nail Fungus
A common fungal infection of the nails
Quick Facts
- Type: Fungal infection of the nail
- Most affected: Toenails
- Common signs: Thick, discolored, brittle nails
- Treatment: Often takes months
Overview
Nail fungus, known medically as onychomycosis, is a common infection in which fungi invade a fingernail or toenail. It usually begins as a small spot of discoloration under the tip of the nail and can gradually spread, causing the nail to thicken, change color, and become brittle.
Toenails are affected far more often than fingernails, partly because they spend time in the warm, moist environment inside shoes, where fungi thrive. Nail fungus is usually not painful at first and is often considered a cosmetic concern, but it can become uncomfortable and is notoriously slow and stubborn to treat. People with diabetes or weakened immune systems may need closer attention because infections can lead to complications.
Symptoms
Nail fungus tends to develop gradually. Common signs include:
- Thickening of the affected nail.
- Discoloration, with the nail turning white, yellow, brown, or even greenish.
- Brittle, crumbly, or ragged nails.
- Distortion in the shape of the nail.
- Debris building up under the nail.
- A slightly foul odor in some cases.
- The nail separating from the nail bed, which can be uncomfortable.
The infection often starts at the edge or tip of one nail and may spread to other nails over time. Pain is usually mild or absent early on but can develop as the nail thickens.
Causes
Nail fungus is caused by various fungal organisms. The most common are dermatophytes, the same group that causes athlete's foot and ringworm. Yeasts and molds can also infect nails. Fungi enter through:
- Small cracks in the nail or breaks in the surrounding skin.
- Spread from an existing athlete's foot infection to the toenails.
- Contact with contaminated surfaces, such as floors in public showers, locker rooms, and pool areas.
- Sharing nail tools or wearing shoes that harbor fungi.
Once inside the warm, moist space under the nail, fungi find an ideal environment to grow, which is part of why the infection can be persistent.
Risk Factors
Several factors increase the likelihood of nail fungus:
- Older age, as nails grow more slowly and circulation may decline.
- Sweating heavily or wearing tight, non-breathable footwear.
- Athlete's foot or other fungal skin infections.
- Walking barefoot in communal damp areas.
- Minor nail or skin injuries.
- Diabetes, poor circulation, or a weakened immune system.
Diagnosis
A clinician can often suspect nail fungus from the nail's appearance, but other conditions, such as psoriasis or nail injury, can look similar. To confirm the diagnosis, the doctor may:
- Take nail clippings or scrape debris from under the nail.
- Examine the sample under a microscope.
- Send a sample for fungal culture to identify the specific organism.
Confirming that fungus is truly present is helpful before starting long courses of oral medication, since these treatments carry some risks and take months to work. Identifying the type of fungus can also guide the most effective therapy.
Treatment
Nail fungus can be difficult to clear, and treatment often takes several months because the nail must grow out. Options include:
- Oral antifungal medications, which are usually the most effective for clearing the infection and are taken for several weeks to months. Liver function may be monitored during treatment.
- Topical antifungal lacquers, solutions, or creams, applied to the nail, which work best for mild or surface infections but require consistent, long-term use.
- Trimming and thinning the nail, sometimes combined with medication.
- Removal of the nail in severe or resistant cases.
Even after successful treatment, nail fungus can return, so ongoing foot care and prevention are important. Completing the full course of treatment improves the chance of a lasting cure.
Prevention
Steps to lower the risk of nail fungus and prevent recurrence include:
- Keep nails trimmed, clean, and dry.
- Wear breathable shoes and moisture-wicking socks, and change socks when they become damp.
- Wear sandals or flip-flops in public showers, locker rooms, and around pools.
- Treat athlete's foot promptly to prevent it from spreading to the nails.
- Do not share nail clippers or files, and disinfect tools.
- Alternate shoes to let them dry out, and consider antifungal powders.
When to See a Doctor
See a healthcare provider if:
- Self-care and over-the-counter products do not improve the nail.
- The nail becomes painful, thickened, or distorted.
- The infection spreads to other nails or the surrounding skin.
- You have diabetes, poor circulation, or a weakened immune system, since even minor foot problems can become serious in these situations.
People with diabetes should pay close attention to any nail or foot changes and seek prompt care, because infections of the feet can lead to complications if not treated early.
Frequently Asked Questions
Why is nail fungus so hard to get rid of?
Fungi live in the warm, moist space under the nail and are shielded by the hard nail itself, so medications take time to reach and clear them. Treatment often lasts months because the infected nail must grow out, and the infection can return even after it clears.
Can I treat nail fungus with over-the-counter products?
Over-the-counter antifungal products can help mild, surface-level infections but often are not strong enough for established nail fungus. If the nail is thick, discolored, or worsening, see a healthcare provider, who may recommend prescription topical or oral antifungal treatment.
Is nail fungus contagious?
Yes, it can spread. The fungi can pass between nails, from athlete's foot to the toenails, and through contaminated surfaces like locker room floors or shared nail tools. Good foot hygiene and not sharing clippers help prevent spread.
How long does treatment take?
Treatment usually takes several months. Oral antifungals are often taken for several weeks, but the nail can take many months to grow out and look normal. Topical treatments require consistent daily use over a long period.
When should someone with diabetes worry about nail fungus?
People with diabetes should have any nail or foot changes checked promptly, because reduced circulation and nerve changes make foot infections more likely to cause complications. Early evaluation and careful foot care are important to prevent more serious problems.
References
- Mayo Clinic. Nail fungus.
- American Academy of Dermatology.
- MedlinePlus, U.S. National Library of Medicine.
- Centers for Disease Control and Prevention (CDC). Fungal Diseases.