Causes of Candidiasis (Thrush)

Candida infection is a fungal infection caused by yeast.

Candida species, over 20 in number, are normal inhabitants of the mouth, throat, vagina and other mucosal surfaces like the gastrointestinal tract. These are small in number and do not cause harm.

Sometimes they may multiply to cause infections. Commonest culprit is the Candida albicans species. (1)

In women, yeast infections are one of the commonest reasons for vaginal discharge, burning, stinging and itching.

These yeasts are a part of the normal environment of the vagina. Infection occurs when there is a disbalance of this environment causing them to multiply.

The disbalance may be due to change in acidity of the vagina or the hormonal balance of the vagina. This is the commonest cause for infection.

80-90% cases are caused by Candida albicans.

Common causes of Candidiasis

Common causes of thrush include pregnancy, menstruation, birth control pills, diabetes, steroid or antibiotic use.

After menopause there is a heightened risk of candida infections.

Those with a weak immunity are also prone to vaginal candidiasis.

Candida infections rarely may also be passed from person to person via unprotected sexual intercourse. (2)

Causes of Invasive Candidiasis

Invasive candidiasis occurs when there is suppressed immunity. This leads to multiplication of the candida that the person harbors normally and their entry into the blood stream.

Candida in invasive candidiasis may also be acquired from medical devices like intravenous (IV) catheters etc. (2)

Candidiasis risk factors

Risk factors that raise the possibility of getting candidial infections include (3) –

  • Taking antibiotics – The vagina and gastrointestinal tract is colonized by friendly bacteria called commensal organisms. Taking antibiotics kill these and alter the normal environment that allows unchecked growth of the yeast.
  • Taking steroids – Steroids suppress the immunity and may allow candidial growth.
  • Pregnancy.
  • Diabetes – There is too much sugar in the blood and a weakened immunity that raises the risk of thrush.
  • Weak immune system due to diseases like AIDS, blood and other cancers. In cancers chemotherapy is a cause behind thrush. Since immunity is low the person is unable to fight of the yeast infection.
  • Elderly with low immunity.
  • New born babies especially if they are born with a low birth weight.

Further Reading

Last Updated: May 31, 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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