Medically reviewed by Dr. Tom Biernacki, DPM
Board-certified podiatric surgeon | Balance Foot & Ankle, Howell & Bloomfield Hills, MI
Last reviewed: May 2026
Quick answer: What Causes Toenail Fungus is a common nail condition with multiple causes including trauma, fungal infection, biomechanical pressure, and underlying medical conditions. Treatment depends on the cause: trauma resolves as the nail grows out (6-12 months), fungus needs antifungal therapy, and biomechanical issues need shoe and orthotic correction. Call (810) 206-1402.
Medically reviewed by Dr. Tom Biernacki, DPM
Board-certified podiatric surgeon | Balance Foot & Ankle
Last reviewed: April 2026
Understanding what causes toenail fungus is the first step toward actually getting rid of it — and more importantly, preventing it from coming back. In our clinic, we see patients who’ve cleared an infection only to get re-infected within months because they never addressed the source. The fungus is almost always coming from somewhere specific in their environment or routine.
The most important clinical decision with What Causes Toenail Fungus isn’t which treatment to start with — it’s identifying the correct subtype. That changes everything. Call (810) 206-1402.
The most important clinical decision with What Causes Toenail Fungus isn’t which treatment to start with — it’s identifying the correct subtype. That changes everything. Call (810) 206-1402.
The Main Cause of Toenail Fungus
Toenail fungus is caused by microscopic fungi that invade the nail plate or nail bed. The most common culprit — responsible for about 90% of cases — is Trichophyton rubrum, a dermatophyte (a type of fungi that feeds on keratin, the protein that makes up nails and skin). Less commonly, toenail fungus is caused by other dermatophytes (T. interdigitale), non-dermatophyte molds (like Fusarium and Aspergillus), or yeasts (Candida).
These organisms are everywhere in our environment — soil, surfaces, and the skin of other people. The question isn’t whether you’re exposed; it’s whether the fungus can get a foothold. That depends on your nail health, immune system, and environment.
How Does Toenail Fungus Enter the Nail?
Fungi can’t penetrate healthy, intact nail tissue from above. They need a portal of entry — usually one of the following:
- The distal (free) edge of the nail — the most common entry point; the gap between the nail edge and the nail bed allows fungal spores to penetrate and work their way up
- Trauma to the nail — even minor trauma (stubbing a toe, tight shoes that press on the nail) creates microscopic separations in the nail-bed junction
- Onycholysis — if the nail is lifting away from the nail bed for any reason, that gap becomes a direct fungal highway
- Adjacent skin infections — athlete’s foot (tinea pedis) spreads to the nail plate from infected surrounding skin, particularly around the lateral nail folds
Who Is Most at Risk?
While anyone can develop toenail fungus, certain factors dramatically increase susceptibility:
- Age: people over 60 have 3–4x higher rates; nails grow slower, thicken naturally, and circulation decreases with age
- Diabetes: impaired immune response and circulation make the feet highly vulnerable to fungal infection
- Poor circulation (peripheral arterial disease): reduced blood flow diminishes the immune defense delivered to the nail
- Weakened immune system: HIV, immunosuppressive medications (post-transplant, chemotherapy), or autoimmune conditions
- Previous nail trauma: even minor injuries create entry points for fungi
- Athlete’s foot history: tinea pedis almost always precedes or accompanies nail infection — the skin and nail share the same organism
- Sweaty feet (hyperhidrosis): warm, moist conditions accelerate fungal growth
- Narrow toe box footwear: high heels or pointed shoes crowd toes, creating micro-trauma and limited air circulation
- Family history: genetic susceptibility to fungal infections is well-documented
Key takeaway: The most preventable cause of toenail fungus recurrence: not treating athlete’s foot. If you clear your nails but leave tinea pedis on the surrounding skin, re-infection of the nail is almost guaranteed. Always treat the skin and the nail simultaneously.
Where Do People Pick Up Toenail Fungus?
Specific environments where fungal transmission is most common:
- Swimming pools and pool decks — wet surfaces, barefoot traffic, and warm temperatures create ideal fungal breeding grounds
- Gym locker rooms and showers — high-traffic wet areas; fungal spores survive on surfaces for extended periods
- Nail salons — improperly sterilized tools (nail clippers, files, drill bits) can transfer fungi between clients
- Public showers at hotels, gyms, spas — even brief barefoot exposure on contaminated surfaces can trigger infection
- Shared footwear — borrowing someone’s shoes, socks, or even trying on shoes at a store without socks
- Within your own household — the bathtub or shower floor is one of the most common sources of self-reinfection and family transmission
Does Nail Polish Cause Toenail Fungus?
Dark or opaque nail polish doesn’t cause fungus on its own, but it creates conditions that support fungal growth: it blocks light, traps moisture under the nail, and prevents you from monitoring nail changes early. Keeping nails polished continuously without breaks is a known risk factor for nail fungus development and recurrence after treatment. If you wear nail polish, we recommend periods of 2–4 weeks with bare nails, and always use a clean base coat.
Preventing Toenail Fungus
- Always wear sandals or water shoes in public wet areas — pools, locker rooms, hotel showers
- Keep nails short and trimmed straight across
- Change socks daily; choose moisture-wicking materials over cotton
- Rotate shoes to allow complete drying between wears
- Disinfect nail clippers with 70% isopropyl alcohol before use
- Treat athlete’s foot promptly — don’t let skin infections reach the nail
- Apply antifungal spray to the inside of shoes regularly
- Choose salons that sterilize instruments in an autoclave or use single-use tools
- If you have diabetes, have a podiatrist examine your nails at every visit
Frequently Asked Questions
Can toenail fungus spread to other nails?
Yes — without treatment, toenail fungus spreads to adjacent nails by direct contact and through contaminated footwear and socks. The mechanism is the same as original infection: the organism spreads from infected nail or skin to an adjacent nail’s entry points. Treating early minimizes spread.
Is toenail fungus caused by poor hygiene?
Poor hygiene is one contributing factor, but it’s not the primary cause. Many people with excellent hygiene develop nail fungus simply from brief barefoot exposure in a high-risk area. Immune status, nail health, and genetics are more important determinants than hygiene alone.
Can you get toenail fungus from shoes?
Yes — fungal organisms survive in the warm, dark interior of shoes. If you’ve been treated for nail fungus but continue wearing the same shoes without disinfecting them, re-infection is common. Treat shoes with antifungal spray or UV shoe sanitizers, and discard very old footwear if infection keeps recurring.
Dr. Tom’s Nail & Foot Hygiene Kit
Moisture is fungus fuel. FLAT SOCKS keeps your shoes dry — antimicrobial, moisture-wicking liner for any shoe. The barefoot feel without the sweat and odor.
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For nail bed soreness and surrounding skin pain during fungal treatment. Arnica + menthol, plant-based, FSA-eligible. Apply to relieve discomfort as nails grow out.
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Sources
- Gupta AK, Nakrieko SA. Onychomycosis infections: do laboratory results predict clinical response in patients. J Am Podiatr Med Assoc. 2015.
- Sigurgeirsson B, Baran R. The prevalence of onychomycosis in the global population. J Eur Acad Dermatol Venereol. 2014.
- Ghannoum MA, Hajjeh RA. Overview of fungal infections. Clin Infect Dis. 2000.
- American Academy of Dermatology. Nail fungus: who gets and causes. aad.org. 2025.
When Shoes Aren’t Enough — Dr. Tom’s Top 9 Orthotics
About 30% of patients I see for foot pain need MORE than a great shoe — they need a structured insole. Below: my complete 2026 orthotic ranking with pros, cons, and the specific patient I’d give each one to.
★ DR. TOM’S COMPLETE 2026 ORTHOTIC RANKING
9 Best Prefab Orthotics by Use Case
PowerStep, CURREX, Spenco, Vionic, and Tread Labs — every orthotic I’ve fitted to thousands of patients across both Michigan offices. Each card includes pros, cons, and the specific patient I’d give it to. Real Amazon ratings, review counts, and prices below.
Best All-Purpose Orthotic for Most Patients
Semi-rigid arch shell + dual-layer cushion + deep heel cup. The orthotic I’ve fitted to more patients than any other for 15 years. APMA-accepted. Trim-to-fit design works in athletic shoes, casual shoes, and most work boots.
Watch: Tea Tree Oil Toenail Fungus Home Treatment [Doctor Cure!] — MichiganFootDoctors YouTube
✓ Pros
- Semi-rigid arch shell provides true biomechanical correction
- Deep heel cup centers the heel and reduces lateral instability
- Dual-layer cushion (top + bottom) lasts 9-12 months daily wear
- Available in 8 sizes for precise fit
- APMA-accepted and clinically validated
- APMA-accepted with superior cushioning versus rigid alternatives
✗ Cons
- Too thick for most dress shoes (use ProTech Slim instead)
- Some break-in period required (3-7 days for arch tolerance)
- Not enough correction for severe pes planus or rigid pes cavus
Dr. Tom’s Recommendation: If a patient has run-of-the-mill plantar fasciitis, mild flat feet, or arch fatigue, this is the first orthotic I try. Better value than most premium alternatives for 90% of patients, which is why it’s the first orthotic I reach for in the clinic. Sub-$50 typically.
Maximum Motion Control · Flat Feet & Severe Over-Pronation
PowerStep’s most aggressive stability orthotic. Adds a 2°-7° medial heel post on top of the standard PowerStep platform — designed specifically for flat-footed patients and severe pronators who need real corrective force.
✓ Pros
- 2°-7° medial heel post adds aggressive pronation control
- Same trusted PowerStep arch shell, more correction
- Built specifically for flat-foot biomechanics
- Excellent for posterior tibial tendon dysfunction (PTTD)
- Removable top cover for cleaning
✗ Cons
- Too aggressive for neutral-arch patients
- Needs longer break-in (10-14 days) due to stronger correction
- Adds 2-3 mm of stack height — won’t fit slim dress shoes
Dr. Tom’s Recommendation: When a patient comes in with significant flat feet AND symptoms (heel pain, arch pain, knee pain), the Original PowerStep isn’t aggressive enough. The Maxx is what gets prescribed. About 25% of my flat-footed patients end up here.
Low-Profile · Fits Dress Shoes & Narrow Casuals
3 mm slim profile with podiatrist-designed tri-planar arch technology. Engineered specifically to fit inside dress shoes, oxfords, loafers, and women’s flats without crowding the toe box. Vionic was founded by an Australian podiatrist.
✓ Pros
- 3 mm slim profile (vs 7-10 mm for standard orthotics)
- Tri-planar arch technology adds support without bulk
- Built-in deep heel cup despite slim design
- Fits dress shoes WITHOUT having to remove the factory insole
- Trim-to-fit · APMA-accepted
✗ Cons
- Less arch support than full-volume orthotics
- Top cover wears faster than thicker alternatives
- Not enough correction for severe foot deformities
Dr. Tom’s Recommendation: My default when a patient says ‘I need orthotics but I have to wear dress shoes for work.’ Slim enough to fit in oxfords and pumps without the heel sliding out. The single highest-impact change you can make for office workers with foot pain.
Built-In Metatarsal Pad · Morton’s Neuroma · Ball-of-Foot Pain
Standard Pinnacle orthotic with a built-in metatarsal pad positioned proximal to the metatarsal heads — the exact location that offloads neuromas and metatarsalgia. No need for separate met pads or pad placement guesswork.
✓ Pros
- Built-in met pad eliminates DIY pad placement errors
- Specifically designed for Morton’s neuroma + metatarsalgia
- Same trusted PowerStep arch + heel cup platform
- Top cover protects sensitive forefoot skin
- Faster relief than orthotics + add-on met pads
✗ Cons
- Met pad position is fixed (can’t fine-tune individual placement)
- Some patients with very small or very large feet need custom
- Slightly thicker than the standard Pinnacle
Dr. Tom’s Recommendation: If a patient has Morton’s neuroma, sesamoiditis, or generalized ball-of-foot pain (metatarsalgia), this saves a clinic visit and a prescription. The built-in pad placement is anatomically correct for 80% of feet. Way better than DIY met pads.
Adaptive Dynamic Arch · Athletic & Daily Wear
Currex’s flagship adaptive arch technology — the orthotic flexes with your gait instead of fighting it. Different stiffness zones along the length give you targeted support at the heel, midfoot, and forefoot. Available in three arch heights (low/medium/high).
✓ Pros
- Dynamic flex zones adapt to natural gait cycle
- Three arch heights ensure precise fit
- Lighter than rigid orthotics (no ‘heavy foot’ feel)
- Excellent for runners and athletic walkers
- European podiatric design (German engineering)
✗ Cons
- More expensive than PowerStep Original ($55-65 typically)
- Less aggressive correction than Pinnacle Maxx for severe cases
- Three arch heights means you must self-select correctly
Dr. Tom’s Recommendation: I started recommending Currex three years ago for runners who said PowerStep felt ‘too rigid.’ The dynamic flex zones respect natural gait. Best for active patients who walk 8K+ steps daily and don’t need maximum motion control.
Running-Specific · Heel Strike + Forefoot Strike Compatible
Currex’s purpose-built running orthotic. The midfoot flex zone is positioned for runner’s gait mechanics, with a flared heel cushion for heel strikers and a forefoot rocker for midfoot/forefoot strikers. Tested on 1000+ runners during product development.
✓ Pros
- Designed by German biomechanics lab specifically for runners
- Dynamic arch flexes with running gait (not static like PowerStep)
- Three arch heights (low/medium/high)
- Reduces overuse injury risk in mid-distance runners
- Lightweight (no impact on cadence)
✗ Cons
- Premium price ($60-75)
- Not aggressive enough for severe over-pronators (use Pinnacle Maxx)
- Runner-specific design = less ideal for daily walking shoes
Dr. Tom’s Recommendation: If a patient runs 20+ miles per week and has plantar fasciitis or shin splints, this is the orthotic I prescribe. The dynamic flex zones respect running biomechanics in a way that no rigid PowerStep can match. Pricier but worth it for serious runners.
Cavus Foot & High-Arch Patients
Polyurethane base with a deeper heel cup and higher arch profile than PowerStep — built for cavus (high-arched) feet that need maximum cushion and support. The 5-zone cushioning system addresses the unique pressure points of high-arch feet.
✓ Pros
- Deeper heel cup centers the heel for cavus foot stability
- Higher arch profile fills the void under high arches
- 5-zone cushioning addresses cavus foot pressure points
- Polyurethane base lasts 12+ months
- Available in Wide width
✗ Cons
- Too tall/aggressive for normal or low arches
- Won’t fit slim dress shoes
- Pricier than PowerStep Original
- Some patients find the arch height uncomfortable initially
Dr. Tom’s Recommendation: Cavus foot patients are often misdiagnosed and given low-arch orthotics — that makes everything worse. Spenco’s Total Support has the arch profile that high-arch feet actually need. About 15% of my patients have cavus feet; this is what they wear.
Cushion Layer · Standing All Day · Gel Pressure Relief
NOT a true biomechanical orthotic — this is a cushion insole. But for patients who want gel pressure relief instead of arch correction (or to add ON TOP of factory insoles in work boots), this is the best gel option on Amazon.
✓ Pros
- Genuine gel cushioning (not foam pretending to be gel)
- Targeted gel waves under heel and ball of foot
- Trim-to-fit · works in most shoe types
- Sub-$15 price (most affordable option in this list)
- Massaging texture is genuinely soothing
✗ Cons
- ZERO arch support — this is cushion only
- Won’t fix plantar fasciitis or flat-foot issues
- Compresses faster than PowerStep (4-6 months)
- Top cover wears through in high-mileage applications
Dr. Tom’s Recommendation: I recommend these to patients who tell me ‘I just want my feet to stop hurting at the end of my shift’ and who don’t have a biomechanical issue. Construction workers, factory workers, retail. Pure cushion does the job for them.
Tight-Fitting Shoes · Cycling Shoes · Hockey Skates
Tread Labs Pace insole with firm orthotic arch support for flat feet and plantar fasciitis relief. The replaceable top cover design makes it one of the most durable picks in this guide — backed by a million-mile guarantee and recommended for tight-fitting athletic footwear.
✓ Pros
- Firm orthotic arch support shell (podiatrist-grade)
- Slim profile fits tight athletic footwear
- Lasts 12+ months daily wear
- Excellent for cycling shoes specifically
- Built-in odor-control treatment
✗ Cons
- Premium price ($45-55)
- Less cushion than PowerStep equivalents
- Not as aggressive correction as Pinnacle Maxx for flat feet
- The signature ‘heel cup feel’ takes 1-2 weeks to adapt to
Dr. Tom’s Recommendation: If you’re a cyclist with foot numbness, hot spots, or knee pain — this is the orthotic. The stabilizer cap solves cycling-specific biomechanical issues that no other orthotic addresses. Worth the premium for athletes.
None of these solving your foot pain?
Some patients (about 30%) need custom-molded prescription orthotics. We make 3D-scanned custom orthotics in our Howell and Bloomfield Hills offices — specifically built for your foot mechanics.
Schedule a Custom Orthotic Fitting →FSA/HSA eligible · Most insurance accepted · (810) 206-1402
What is Toenail fungus?
Toenail fungus is a common foot/ankle condition that affects mobility and quality of life. Understanding the underlying cause is the first step in successful treatment. Our podiatrists at Balance Foot & Ankle perform a hands-on biomechanical exam, review your activity history, and use diagnostic imaging when appropriate to identify the root cause—not just treat the symptom. Many patients have been told to “rest and ice” without a deeper diagnostic workup; our approach is different.
Symptoms and warning signs
Common signs of toenail fungus include pain that worsens with activity, morning stiffness, swelling, tenderness when palpated, and difficulty bearing weight. If you experience sudden severe pain, inability to walk, visible deformity, numbness or color change, contact our office the same day or visit urgent care—these can signal a more serious injury such as a fracture, tendon rupture, or vascular compromise. Diabetics with any foot wound should seek same-day care.
Conservative treatment options
Most cases of toenail fungus respond to non-surgical care: structured rest, supportive footwear changes, custom orthotics, targeted stretching and strengthening protocols, anti-inflammatory medications when medically appropriate, and in-office procedures such as ultrasound-guided injections. We also offer advanced therapies including MLS laser therapy, EPAT/shockwave, regenerative injections, and image-guided procedures. Treatment is sequenced from least invasive to most invasive, and we explain the rationale at every step.
When is surgery considered?
Surgery is reserved for cases that fail 3-6 months of well-structured conservative care, when there is structural pathology (severe deformity, complete tear, advanced arthritis), or when imaging shows damage that will not heal without intervention. Our surgeons have performed 3,000+ foot and ankle procedures and prioritize minimally-invasive techniques whenever appropriate. We discuss recovery timelines, return-to-activity milestones, and realistic outcome expectations before any procedure is scheduled.
Recovery timeline and prevention
Recovery from toenail fungus varies based on severity and chosen treatment path. Conservative cases often improve within 4-8 weeks with consistent adherence to the protocol. Post-procedural recovery may range from a few days (in-office procedures) to several months (reconstructive surgery). Long-term prevention involves footwear assessment, activity modification, structured strengthening, and regular check-ins with your podiatrist if you have a history of recurrence. We provide written home-exercise plans and digital follow-up support.
Ready to feel better?
Same-week appointments available in Howell and Bloomfield Hills, Michigan.
Book Your VisitIn-Office Treatment at Balance Foot & Ankle
If home treatment isn’t providing relief for your toenail issues, our podiatry team at Balance Foot & Ankle can help with same-day evaluations and advanced in-office care.
American Academy of Dermatology: Nail Fungus
Ready to Get Relief?
Same-day appointments available in Howell & Bloomfield Hills, MI
4.9★ | 1,123 Reviews | 3,000+ Surgeries
Or call: (810) 206-1402
Dr. Tom Biernacki, DPM is a board-certified foot & ankle surgeon (ABFAS & ABPM) at Balance Foot & Ankle Specialists in Southeast Michigan. With over a decade of clinical experience, he specializes in heel pain, bunions, diabetic foot care, sports injuries, and minimally invasive surgery. Dr. Biernacki is a member of the APMA and ACFAS, and his patient education content on MichiganFootDoctors.com and YouTube has made him one of the most-followed foot & ankle educators on YouTube.