Causes of fungal nail infections

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Fungal nail infections are one of the most common dermatological conditions in the United Kingdom. Nearly 3 in 100 in the UK suffer from fungal nail infections at some point in their lives.

In the UK the prevalence of fungal nail infections is as high as 26.9%. In the United States the prevalence of the condition is 18.5% and is said to be on the rise.

Why is the number of fungal nail infections on the rise?

The rise is due to the rising numbers of people with diabetes and poor immunity. Also since this condition affects the elderly the rise is due to increasing numbers of aging individuals.

Who is affected by fungal nail infections?

Fungal nail infections, also called onychomycosis, are the reason behind half of all nail disorders and one third of skin fungal infections. Toenails are more commonly affected than fingernails. Elderly are more commonly affected than the young.

Fungal nail infections affect 32% of people between ages 60 and 70, and 48% of the population may be affected by age 70. In the young those sharing communal baths and showers like swimmers and athletes or long distance runners are particularly at risk.

Causes and risk factors of fungal nail infections

Causes and risk factors of getting fungal nail infections include (1-5):

  • Those with fungal skin infections. Athlete’s foot is a fungal skin infection of the skin between the toes. This infection left untreated often spreads to toenails.
  • Fungal skin infections are responsible for spread to finger nails due to scratching the lesions and spread of the fungal spores to the finger nails.

Fingernail infection may occur after a toenail infection has become established. This also occurs due to excessive scratching.

  • Damaged and broken nails allow fungi to infect them. Constant nail biting and use of artificial and cosmetic nails may also raise the risk of fungal nail infections.
  • Those who wash hands repeatedly e.g. cleaners, cooks and other occupations where working with water for long durations is necessary are also at risk.

Constant washing may damage the protective skin at the base of the nail. This may allow fungi to enter and infect the nails.

  • Individuals living in hot and humid climates are at an increased risk.
  • Those with chronic health conditions are at risk of fungal nail infections. This includes individuals with:
    • diabetes
    • psoriasis
    • poor blood circulation in the fingers and toes
    • suppressed or poor immune system for example in individuals with AIDS or those on cancer or other chemotherapy
    • those with a generally poor state of health
  • Smokers also have a high risk of fungal nail infections. This could be due to poor blood circulation in fingers and toes due to long term smoking.
  • Age of the person is a risk factor. Adults are nearly 30 times more likely than children to suffer the condition. Fungal nail infections affects 2.6% of children younger than 18 years, but as many as 90% of people older than 70 years.
  • Sometimes the cause of the infection is unknown and perfectly healthy individuals may get fungal nail infections due to contact with other people with the infection.

Organisms that lead to fungal nail infections

Organisms that lead to fungal nail infections include (2, 3):

  • Dermatophytes – this includes Trichophyton rubrum or Trichophyton mentagrophytes that causes over 90% of cases. Of these T. rubrum is responsible for about 70% cases.
  • Epidermophyton spp. and Microsporum spp. are other organisms that may cause fungal nail infections.
  • Around 8% (5 to 17% cases) of total infections is caused by yeast infections like Candida albicans in the UK and Malassezia furfur in tropical countries.
  • Some Non-dermatophyte moulds like Scopulariopsis brevicaulis, Acremonium spp and Fusarium spp. may lead to 3 to 5% of infections.

Further Reading

Last Updated: Apr 22, 2019

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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