What causes oral candidiasis (thrush)?

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From the Guidelines

Thrush is primarily caused by an overgrowth of Candida albicans, triggered by factors such as antibiotic use, weakened immune systems, corticosteroid use, dentures, smoking, and hormonal changes, as well as poor oral hygiene, dry mouth conditions, and high-sugar diets 1. These factors disrupt the natural balance of bacteria and yeast in the body, allowing Candida albicans to multiply rapidly and cause thrush. Some of the key factors that contribute to the development of thrush include:

  • Antibiotic use, which disrupts the normal bacterial balance in the body 1
  • Weakened immune systems, such as those caused by HIV/AIDS, cancer, or diabetes 1
  • Corticosteroid use, including inhaled steroids for asthma 1
  • Dentures, especially ill-fitting ones 1
  • Smoking 1
  • Hormonal changes, such as those that occur during pregnancy 1
  • Poor oral hygiene 1
  • Dry mouth conditions 1
  • High-sugar diets 1 It is essential to address these underlying factors to prevent the development of thrush and to manage the condition effectively. Maintaining good hygiene, limiting sugar intake, managing underlying conditions like diabetes, and rinsing your mouth after using steroid inhalers can help prevent recurrence of thrush 1. Additionally, treatment with antifungal medications like nystatin oral suspension or fluconazole tablets can help to clear up the infection 1. For vaginal thrush, over-the-counter clotrimazole or miconazole creams or suppositories can be effective 1. It is crucial to note that thrush can be a sign of an underlying condition, such as a weakened immune system, and therefore it is essential to seek medical attention if symptoms persist or recur 1.

From the Research

Causes of Thrush

Thrush, also known as oral candidiasis, can be caused by various factors, including:

  • Immunocompromised state, such as in HIV-positive patients 2, 3, 4, 5
  • Diabetes 3
  • Broad-spectrum antibiotics 3
  • Corticosteroid use 3
  • Presence of dentures 3
  • Weakened immune system, which can be due to various reasons such as immunosuppressive therapy or certain medical conditions 6
  • Overgrowth of Candida species, which are normally present in the mouth and can become pathogenic under certain conditions 6

Risk Factors

Certain individuals are more prone to developing thrush, including:

  • Neonates, who can develop thrush due to exposure to Candida during birth 3
  • People with a history of oral candidiasis 4
  • Those who have taken antifungal drugs in the past 4
  • Individuals with a low CD4 count, which indicates a weakened immune system 2

Underlying Conditions

Thrush can also be associated with underlying conditions, such as:

  • Crohn's disease, which can lead to an overgrowth of Candida in the gut 6
  • Certain types of neurological disorders, which can also be linked to an overgrowth of Candida 6

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Treatment of oropharyngeal candidiasis in HIV-positive patients.

Journal of the American Academy of Dermatology, 1994

Research

Candidiasis (oropharyngeal).

BMJ clinical evidence, 2012

Research

Candida Pathogenicity and Interplay with the Immune System.

Advances in experimental medicine and biology, 2021

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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