Outpatiented · Case Knowledge
A patient with a fungal nail infection wants to know if it is contagious, whether it is safe to travel, and what to do about the acrylic nails. The infection gets called ringworm, which is the wrong name and matters, because the right name tells you what the treatment is and what the actual risk looks like.
Getting the Name Right
Ringworm is tinea corporis, a dermatophyte (fungal) infection of the skin that produces a ring-shaped rash. It does not infect nails. The circular pattern gave it the misleading name 'ringworm,' but there is no worm involved. It is a fungus.
Fungal nail infection is tinea unguium, also called onychomycosis. It is caused by the same family of fungi (dermatophytes, most commonly Trichophyton rubrum) but it lives in and under the nail plate, a structurally different environment than skin that requires a different treatment approach.
The distinction matters practically: treatments that work for skin ringworm (topical antifungals applied to the surface) largely fail for nail fungus because they cannot penetrate the nail plate adequately. Getting the diagnosis right determines whether the treatment has any chance of working.
Contagiousness. The Real Risk
Tinea unguium has low-to-moderate transmission risk. Understanding what that means practically is more useful than a simple yes-or-no answer.
Dermatophytes spread through direct skin and nail contact or through shared fomites, surfaces that can harbor the fungus, including nail files, clippers, nail scissors, bath mats, and shared shower floors. The fungus is not airborne. Normal social contact, hugging, shaking hands, carries minimal risk. The risk concentrates in shared moist environments and shared nail care tools.
Intact skin provides a significant barrier against dermatophyte invasion. The organisms need a point of entry, small cuts, abrasions, skin macerated by prolonged moisture, or areas of compromised skin integrity. A granddaughter with healthy intact skin who is not sharing nail tools and who practices basic hygiene when bathing has a low, not zero, risk of transmission.
Bath mats, shower floors, and bathtubs are the surfaces most likely to harbor dermatophytes in a household setting. Using separate bath mats, cleaning the shower or tub before others use it, and not sharing towels are practical risk-reduction measures. These do not need to be elaborate. They just need to be consistent.
Nail files, clippers, and scissors are direct fomite transmission routes. The infected person's nail care tools should be personal and used by no one else. This is the single highest-risk transmission route in a household and the easiest to eliminate completely.
Basic hygiene eliminates the highest-risk transmission routes.
Travel this weekend with reasonable precautions is appropriate.
The Acrylic Nail Problem
Acrylic nails create a sealed, warm, moist environment over the nail plate, conditions that are optimal for fungal growth and that actively work against any treatment being applied. The fungus grows more aggressively under acrylics than it would with natural nails exposed to air.
Acrylic nails also create small gaps and micro-spaces at the nail margins where moisture collects and cannot dry out. These gaps become reservoirs for the dermatophyte. Even if oral antifungal treatment is started, the acrylic environment makes clearing the infection substantially harder.
Removing the acrylics is not optional as part of effective treatment. It is a prerequisite. Treatment initiated while acrylics remain in place has a meaningfully lower chance of success and a higher rate of recurrence.
Treatment
The nail plate is a dense, keratinized structure that topical antifungal creams and lacquers penetrate poorly. The fungus lives at the nail bed and under the plate, beyond where topicals reach at adequate concentrations. This is why over-the-counter treatments and even prescription topical lacquers often fail to clear nail fungus despite months of faithful application.
Terbinafine (Lamisil) taken orally achieves effective concentrations in the nail plate through systemic delivery. It is fungicidal against dermatophytes. It kills the organism rather than just suppressing growth. Standard dosing is 250mg daily for 6 weeks for fingernail infection and 12 weeks for toenail infection. Mycological cure rates are approximately 70-80%. Liver function monitoring is recommended given hepatotoxic potential, though clinically significant liver injury is uncommon. Baseline LFTs before starting and monitoring during treatment is standard.
Itraconazole is a second-line option, used when terbinafine is contraindicated or not tolerated. It can be dosed continuously or as pulse therapy (one week on, three weeks off, repeated for two to three cycles for fingernails). Effective against a broader spectrum of fungi than terbinafine, making it preferable when non-dermatophyte molds are suspected. More drug interactions than terbinafine due to CYP3A4 involvement, medication list review is important before prescribing.
Prescription topical antifungal lacquers (ciclopirox, efinaconazole, tavaborole) have limited ability to penetrate the nail plate and achieve therapeutic concentrations at the nail bed. They are most useful as adjunctive therapy alongside oral treatment or for very early, superficial infections. Over-the-counter topicals (clotrimazole, miconazole) are not effective for nail infections. Using topicals alone for established tinea unguium is unlikely to produce cure and allows the infection to progress.
Even after the fungus is eliminated, the nail must grow out to appear normal. Fingernails grow approximately 3mm per month; full regrowth takes 4-6 months. Toenails grow more slowly, 12-18 months for full regrowth. The infection may appear to persist visually even after treatment is complete because the damaged portion of the nail has not yet grown out. Recurrence is common, keeping nails trimmed, feet dry, and avoiding re-exposure to fungal environments (shared showers, nail salons with inadequate sterilization) reduces recurrence risk.
Questions People Actually Ask
Is nail fungus contagious to family members?
Yes, but the transmission risk is low-to-moderate and manageable with basic precautions. Dermatophytes require direct contact or shared surfaces to spread. They are not airborne. The highest-risk routes in a household are shared nail care tools (files, clippers, scissors) and shared bathing surfaces (shower floors, bath mats).
Eliminating shared nail tools entirely and using separate bath mats while cleaning shower surfaces before others use them reduces risk substantially. Close contacts with intact, healthy skin have a meaningful barrier against infection. Children and elderly individuals with thinner or more fragile skin may have somewhat higher susceptibility.
Why did the topical cream I used not work?
Topical antifungal creams and over-the-counter treatments do not penetrate the nail plate well enough to reach the fungus at the nail bed where it lives. The nail plate is dense and keratinized. It acts as a barrier that prevents adequate drug concentration from reaching the site of infection.
This is not a failure of compliance or effort. It is a pharmacological limitation. The fungus is in a location that requires systemic delivery via an oral medication to achieve therapeutic levels. Oral terbinafine or itraconazole reaches the nail bed through the bloodstream, which topicals cannot.
Do I have to remove my acrylic nails?
Yes. Acrylic nails create a warm, moist, sealed environment over the nail plate that promotes fungal growth and prevents the nail from breathing. They also create micro-gaps at the margins where moisture accumulates, ideal conditions for the dermatophyte to thrive.
Starting oral antifungal treatment while acrylics remain in place significantly reduces the chance of clearing the infection and increases the chance of recurrence. Removing the acrylics is not cosmetically ideal, but it is a necessary step for effective treatment. Once the infection is cleared and the nail has grown out healthy, acrylic application can be reconsidered, though recurrence risk should factor into that decision.
How long does it take to treat nail fungus?
Oral terbinafine is taken for 6 weeks for fingernail infections and 12 weeks for toenail infections. Itraconazole pulse therapy runs for two to three cycles over several months.
After treatment ends, the nail must grow out to appear fully normal. Fingernails take 4-6 months; toenails take 12-18 months. The visual appearance improves gradually as the healthy nail grows in from the base and the damaged nail grows out. Mycological cure, meaning the fungus is gone, can be confirmed by lab culture of nail clippings if there is uncertainty.
Is it safe to travel with nail fungus?
Yes. Nail fungus is not a contraindication to travel and does not pose a public health risk in the way that some infections do. The transmission risk through normal social contact is minimal.
Reasonable precautions while traveling: use flip-flops in shared shower areas (hotel showers, pool areas), avoid shared nail care tools, and bring your own. Keep nails clean and dry. These are the same precautions that reduce household transmission and are easy to maintain while traveling.
The MAP Tool traces your symptoms and history to root cause. Not a diagnosis. A thread to follow.
Start Your Map