Foot Health Glossary

Nail fungus

Onychomycosis
Medically reviewed · Hottinger Podologie, ZurichUpdated: July 2026

Nail fungus (onychomycosis) is a fungal infection of the nail plate, usually caused by dermatophytes. The nail turns whitish-yellow to brownish, thickens and becomes brittle. Onychomycosis practically never heals on its own, and it is contagious, including for neighbouring nails.

Plate · Nail fungus © HOTTINGER PODOLOGIE Healthy Early infection at the free nail edge Advanced: thickened, brittle, discoloured Typical course of onychomycosis
Typical course: the infection usually starts at the free nail edge and moves towards the nail root. The earlier it is treated, the shorter the way back. · Illustration: Hottinger Podologie
Common causes and risks
  • A warm, moist climate inside shoes, sweating, sport
  • Barefoot zones: pools, saunas, changing rooms
  • Previously damaged nails, circulatory disorders, diabetes
  • Untreated athlete's foot spreading to the nail
What you can do yourself

Keep your feet dry (including between the toes), change socks daily and wash them hot, disinfect shoes, wear bathing shoes in barefoot zones. Have early discolouration checked: the smaller the infection, the simpler the treatment.

When to see a podiatrist

With any unclear nail change. In the practice the affected nail is professionally reduced and thinned, which lowers the fungal load and lets active agents penetrate. We also support the course of treatment with laser therapy; extensive infections call for medication coordinated with your doctor. Nail psoriasis and pressure damage look confusingly similar, another reason for a professional look.

Did you know?

A big toenail grows only about one millimetre per month. Until an infected nail has fully grown out healthy, a good year passes. Patience is part of the therapy.

Common questions
How long does treatment take?
As long as a nail needs to grow out, a good year for the big toenail. Regularity and everyday hygiene are decisive.
Is an over-the-counter antifungal polish enough?
For a small, superficial infection it can be. If the nail is thickened or the root is affected, more is needed. A professional assessment brings clarity before months of polish are wasted.
Related terms
Sources & further reading
Hottinger Podologie · Zurich

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Angelika WinklbauerPodiatry & medical foot care
This entry provides general information and does not replace an individual examination.