Fungal nail

Onychomycosis is a fungal infection of the nail. Typically it involves the toenail and dermatophytes and the predominant etiological agent1.


1.   The most common one is distal subungual onychomycosis in most of the cases caused by the dermatophyte Trichophyton rubrum (see Fig. 1).
The infection usually starts at the rim of the nail which turns whitish-yellow. The fungus grows into the nail, causing the nail plate to thicken. The nail becomes brittle and may separate partially or completely from the nail bed which can be very painful. In the worst case the infection can result in a complete loss of the nail2.


2.   The fungus resides INSIDE the nail, not underneath. The dermatophytes invade the middle and ventral layers of the nail plate where the keratin is comparatively soft3. The dermatophytes grow between the layers of keratinaceous cells of the nail plate and can be found anywhere between the ventral or dorsal side of the nail plate (see Fig. 2). The growth rate of these fungi is tailored to their environment. They grow fast enough towards the proximal end of the nail in order to avoid being grown out, but not too fast so as to avoid coming into contact with the host’s (i.e. human’s) immune system in the nail bed which would attack them.


Nail fungus is a progressive disease caused by dermatophytes. It does not disappear by itself. Left untreated it will increasingly get worse. In the worst case the infection can result in the complete loss of the nail. Nail fungus can also be contagious; it can spread from one nail to the other, but also from one person to another. Therefore, it is crucial to treat nail fungus as soon as symptoms are apparent and the pathology has been diagnosed.


Do I have a fungal nail infection?


If you notice the presence of white spots or patches on your nail, or if the nail is turning yellow, growing thicker or becoming brittle, you probably have a fungal nail infection.


Fungal nail infection (onychomycosis) is a progressive disease: if it is left untreated, the infection spreads.


To start with, you may only see white spots or patches on the nail. They only affect the cosmetic appearance of the nail: initially there is no pain. Gradually the fungus spreads throughout the nail. Unless it is treated, it can become (very) painful, and you run the risk of losing the nail permanently.


Contamination: dermatophytes (fungi) thrive in warm, humid environments. They can spread from one fingernail or toenail to another, and from one person to another.
Environments with a high risk of contamination include: showers, changing rooms, trainers and sports shoes, socks, Turkish baths, etc.


If your nail is showing symptoms like the ones in the photographs below, you probably have a fungal nail infection. Consult your chemist or pharmacist immediately.



Onychomycosis affects a large proportion of the population. Up to 14% in North America have a fungal nail infection which many of them ignore.*


The incidence increases with age: onychomycosis is rare in children, but increases significantly in people aged 35 to 59 and is very common in people aged 60 and over. The condition affects men and women alike.


Fungal nail infection is the most common form of nail infection and is responsible for half of all nail-related problems. Most cases of fungal nail infection affect the toenails, especially the big toe; it occurs but is much less common in the fingernails. The warm, humid environment in shoes provides ideal growing conditions for nail fungus.



*Source: Ghannoum MA, Hajjeh RA, Scher R, Konnikov N, Gupta AK, et al. (2000) A large-scale North American study of fungal isolates from nails: the frequency of onychomycosis, fungal distribution, and antifungal susceptibility patterns. J AM Acad Dermatol 43: 641-648. 


The microorganisms that cause onychomycosis – usually dermatophytes – penetrate microscopic fissures in the nail plate, or enter through the soft tissue around the edges of the nail.


Strong, healthy nails protect the tips of fingers and toes from infection.


If your nails are cracked, naturally fragile, or weakened as a result of an injury or trauma, it is easier for dermatophytes to infect a nail.


Dermatophytes grow in warm, humid environments such as bathrooms, changing rooms, swimming pools, trainers or sports shoes etc., which is why these environments pose a relatively high risk of contamination.



Tips for preventing fungal nail infection :

  • Change your socks every day, and wash them at temperatures above 60°.

  • Wash or clean your shoes regularly. Choose shoes that allow your feet to breathe and avoid shoes that make your feet sweat.

  • After washing and rinsing them thoroughly, dry your feet carefully and dry each toe separately.

  • Wear sandals or suitable footwear in changing rooms and communal showers at e.g. health clubs or swimming pools.



1: Borgers et al. 2005. Fungal infections of the skin: infection process and antimycotic therapy. Curr drug targets Vol 6: 849-862.
2: Roberts et. al. 2003. Guidelines for treatment of onychomycosis. Br J Dermatol Vol 148: 402-410.
3: Rashid et al. 1995. Early events in the invasion of the human nail plate by Trichophyton metagrophytes. Br J Dermatol Vol 133: 932-940.