Toenail fungus, or onychomycosis, is a nail infection that can make your toenails thicker, change color, or break apart. It affects about one in 10 people and is common in adults over 60. While fungi are the most common cause, yeasts and molds can also play a part. There are four types of toenail fungus you can have, depending on the cause and symptom severity.
This starts under your nail and usually develops slowly. It breaks down keratin, the protein in nails that keeps them strong and protected against damage. You’re more likely to get this infection:
- As an adult
- If your feet are frequently damp
- You wear tight shoes
- Injure your nails
- Have diabetes or poor circulation
Fungus usually causes this infection. Molds can also cause it, but it’s less common.
Distal Lateral Subungual Onychomycosis
This is the most common form of toenail fungus. It usually starts at the tip or side of your nail, often on your big toe or pinky, and spreads underneath. Early symptoms include a yellow or white streak near the edge or under the nail. As it worsens, it can cause:
- Brittle or crumbly nail edges
- Keratosis, a buildup of a chalky substance under the nail
- Onycholysis, when the nail lifts from the nail bed
Proximal Subungual Onychomycosis
This rare type of toe fungus starts near the cuticle, the skin at the base of the nail, and spreads outward. It progresses quickly and may stem from an underlying immune system condition. Symptoms may include:
- Nail lifting
- Thickening of the nail that moves outward
- White or yellow discoloration near the base of the nail
Total Dystrophic Onychomycosis
Without treatment, subungual onychomycosis can turn into total dystrophic onychomycosis. This can damage the nail plate (the hard part of the nail) or the root (the base of the nail under the skin), making it challenging to treat. It can:
- Cause pain
- Poor shoe fit
- Difficulty walking
- Raise the risk of ulcers, bacterial infections, and gangrene (tissue damage from poor blood flow)
Symptoms can affect the entire nail and include:
- Brittle, crumbling nails that flake or break
- Complete separation from the nail bed
- Changes in nail appearance
- Severe color changes like white, yellow, or brown
This type of toenail fungal infection accounts for about 10% of cases and mainly affects children. It affects the nail’s surface, which makes it easier to treat.
Since it affects the toenail’s surface, it doesn’t cause thickening or lifting. Instead, you may see:
- Chalky or crumbly spots on the outer layer of the nail
- White or black patches
- Thin horizontal lines
Yeasts like Candida albicans cause this. It’s more common if your feet stay damp for long periods. You’re also more likely to develop this type if you:
- Are older
- Have a weakened immune system
- Have chronic (long-term) red, swollen skin around your nails
- Have chronic yeast infections on your skin or mouth
- Wear closed shoes for long hours
- Work in wet environments
Candida infections usually start in the skin around your nail and then spread to the toenail. Redness and swelling around the nail are often one of the first signs. You may also have:
- Thick or oddly shaped nails
- Yellow, white, or brown discoloration
- Nail lifting or falling off
This is another rare form of toenail fungus. It stays inside the nail plate rather than under it.
You may notice white, cloudy, or pale discoloration across the nail surface without nail lifting (onycholysis) or buildup underneath (subungual keratosis).
Your provider can often recognize toenail fungus by looking at your nail’s color, thickness, and shape. Testing confirms the diagnosis and identifies the specific fungus causing the infection.
They may collect a sample near the lifted nail and perform a potassium hydroxide (KOH) prep. This quick, affordable test dissolves skin cells so fungal elements are easier to see under a microscope, and it’s accurate enough to begin treatment if positive.
Your healthcare provider may also order a:
- Culture: Growing the fungus in a petri dish to identify the type
- Periodic acid–Schiff (PAS) stain: Uses dye to highlight fungal cells
- Polymerase chain reaction (PCR): Detects fungal DNA
If you notice nail changes that won’t go away, reach out to a provider. Delaying care may make toenail fungus harder to treat or cause more damage.
Seek care right away if you have a weakened immune system or notice signs of infection, such as:
- Ongoing pain
- Pus or fluid around the nail
- Redness, swelling, or warmth
Toenail fungus treatments may include:
- Medicated nail polish
- Nail removal in severe cases
- Nail trimming or thinning
- Oral or topical (on the skin or nail) antifungals
- Tea tree oil or Vicks VapoRub (research is limited)
Toenail fungus grows in warm, damp places like sweaty socks or tight shoes that don’t let your feet breathe. Nail damage from pressure can also make it easier for fungus to get in.
To lower your risk:
- Avoid going barefoot in hotels, public showers, pools, or gyms
- Change socks at least once a day
- Keep feet clean, dry, and cool
- Let shoes dry between wears, and disinfect them with antifungal spray or UV sanitizer
- Trim nails straight across and clean clippers after each use
- Use antifungal powder or spray if your feet sweat
- Wear breathable shoes and moisture-wicking socks
If you’ve had toenail fungus before, have chronic conditions, or live with someone who has it:
- Clean shared showers well between uses
- Don’t share shoes or nail tools
- Treat athlete’s foot early to stop the spread to your nails
- Use topical antifungals after treatment to reduce recurrence
As you age, nail care can become more challenging. To help prevent developing toenail fungus, consider soaking your feet to soften the nails, ask for help if needed, and wear roomy shoes. It’s also good to schedule regular foot checks if you have diabetes or poor circulation.
Toenail fungus, or onychomycosis, affects one in 10 people and becomes more common with age. There are different types of toenail fungus, and each type can vary in appearance, cause, and severity. A provider can diagnose it through exams or testing. Early treatment and good foot care can help stop the infection and lower the risk of it returning.
