Thrush is a fungal infection that develops in the mouth and throat. It is caused by an overgrowth of Candida, a type of fungus that is naturally found in the mouth, digestive tract, and skin of most people. Normally, Candida is kept under control by other bacteria in the body, but certain illnesses, medications, or stress can disturb the balance and cause the fungus to grow out of control, leading to thrush. Some of the factors that increase the risk of developing thrush include:

• Having a weakened immune system due to illnesses like HIV/AIDS or cancer treatment
• Taking medications like antibiotics, corticosteroids, or drugs that suppress the immune system
• Having certain underlying medical conditions like diabetes, iron deficiency, or vitamin B12 deficiency
• Wearing dentures, especially upper dentures
• Having conditions that cause dry mouth

Thrush is not contagious and can be treated with antifungal medication. If you have thrush, it is important to finish the entire course of treatment, even if the symptoms go away earlier. If you have a weakened immune system, thrush can be more severe and may lead to more serious systemic candida infections if left untreated.