Onychomycosis: Understanding this Fungal Infection of the Nails
Onychomycosis is a fungal infection that mainly affects the nails of the feet, particularly the big toe. This condition, sometimes overlooked, can lead to alterations of the nail such as thickening, a yellow discoloration, or even local inflammation. These symptoms result from the proliferation of opportunistic fungi, often in warm and humid environments favorable to their development.
Onychomycosis can also affect the hands, especially when the infection is caused by yeasts rather than dermatophytes, which are more common on the feet. This pathology is common, affecting about 1 in 10 adults and up to 30% of people over 70 years old.
Characteristic Symptoms Revealing Onychomycosis
Identifying onychomycosis is based on observing several suggestive signs:
- Thickening of the nail with a brittle or crumbly texture.
- Yellow, white, or sometimes black discoloration of the nail plate.
- Partial or total detachment of the nail from the nail bed (onycholysis).
- Aspiration of whitish powdery debris under the nail, often contagious.
- Inflammation and redness around the nail in certain candidal forms.
A particular case: when onychomycosis starts at the base of the nail (proximal form), this may indicate an underlying immune deficiency and requires enhanced medical attention.
Main Causes of Onychomycosis and Favoring Factors
The fungal infection of the nails is mainly due to dermatophyte fungi such as Trichophyton rubrum, which represent about 65% of cases. Yeasts (Candida) and certain molds (Aspergillus) are other responsible agents. These microorganisms proliferate in warm, humid, dark places, notably in swimming pools, locker rooms, or during prolonged wear of waterproof shoes.
Besides infectious causes, several factors favor the establishment and chronicity of onychomycosis:
- Advanced age, as nail growth slows and their resistance decreases.
- Male sex, with men being more frequently affected than women.
- History of foot fungus, known as athlete’s foot, which can contaminate the nails.
- Chronic diseases such as diabetes, circulatory disorders, and immunosuppression.
- Repeated trauma to the nails, especially related to wearing inappropriate shoes.
The role of hygienic environment and personal hygiene cannot be underestimated to prevent the spread of fungi.
Accurate Diagnosis and Differentiation of Onychomycosis
To confirm onychomycosis, the doctor carries out a nail sampling which will be analyzed in the laboratory by:
- Microscopic examination after potassium hydroxide (KOH) treatment.
- Fungal culture to identify the type of fungus.
- Molecular tests (PCR) when cultures are negative but suspicion remains.
This approach is essential to exclude other pathologies such as psoriasis or lichen planus, whose treatment differs entirely.
More information on these tests is available through this article dedicated to the causes and signs of dermatophytes.
Effective Treatments Against Onychomycosis in 2026
Treatment of onychomycosis adapts to the extent of infection and the overall health of the patient:
- Oral medications: terbinafine, itraconazole, or fluconazole are most prescribed to completely eradicate the infection.
- Topical treatments: antifungal nail lacquers based on ciclopirox, efinaconazole, or tavaborole, suitable for limited forms.
- Complementary measures: debridement by a podiatrist to remove the infected part, use of antifungal creams to prevent recurrence.
The duration of treatment is often long, ranging from 2 to 6 months, due to the slow growth of nails. It is crucial not to interrupt the course to avoid relapse. The patient must also adopt strict hygiene measures to limit moisture at the foot level, as advised in this article on foot baths against fungal infections.
In case of failure of drug treatments, surgical removal of the infected nail may be considered.
Tips to Prevent and Limit Recurrence of Onychomycosis
To reduce the frequency of relapses, adopt these simple but effective habits:
- Keep nails short and clean to limit areas conducive to fungal development.
- Dry feet well after showering, especially between the toes, to eliminate moisture.
- Use cotton or natural fiber socks, which better absorb sweat.
- Change shoes regularly and favor well-ventilated ones.
- Avoid walking barefoot in public places such as pools, saunas, or locker rooms.
- Apply a preventive antifungal cream after treatment to limit recurrences.
These measures are detailed in a practical guide on the prevention of foot and nail fungal infections available on Medicial.fr here.
It is essential to consult quickly at the first appearance of signs of onychomycosis to avoid worsening that could lead to painful secondary infections, especially in diabetic patients or those with circulatory disorders, as explained in this article on foot pain related to complications.
