What is Oral Thrush or Candidas?

Candidiasis, more commonly known as a yeast infection or thrush, is caused by the fungus Candida and is not just limited to the vagina. Thrush can also affect the penis, anus and rectum, oral cavity, and elsewhere in the human body. In fact, oral thrush is one of the most common of all fungal infections affecting the membranes or skin inside the mouth.

Thrush is not uncommon among sexually active gay men, and immunocompromised patients like people living with HIV are particularly susceptible to thrush, including oral thrush. The British Journal of Medicine reported that Candida albicans (C. albicans) is the cause of roughly 80 percent of oral infections, and 90 to 95 percent of folks living with HIV suffer from particularly high colonization rates of C. albicans.

There are multiple variants of oral thrush, but the most common are pseudomembranous, erythematous, and chronic hyperplastic candidiasis. 

Pseudomembranous thrush is common in chronically ill patients and infants, but also impacts all age groups. Individuals with this form of oral thrush develop plaques on the surface of their tongue and the buccal mucosa (the skin of the cheeks and lips inside the mouth). These plaques look like small curds and are masses of fungal strands, dead skin and tissue cells, and bacteria among others. When wiped away, the plaques leave a sore, reddened area.

Erythematous candidiasis is more commonly known as antibiotic sore mouth and afflicts patients who use broad-spectrum antibiotics or corticosteroids. Patients will suffer painful red lesions on the tongue, which are sometimes called kissing lesions when they appear on the palate after coming in contact with an infected tongue.

Chronic hyperplastic candidiasis, also known as candidal leukoplakia, is characterized by “firm white persistent plaques on lips, tongue, and buccal mucosa.” While not as common as other forms of oral thrush, the plaque associated with chronic hyperplastic candidiasis is considered to have premalignant or precancerous potential.

Oral thrush can be treated with topical antifungals and/or oral medications. Topical antifungals have the benefit of reduced systemic exposure and fewer adverse drug reactions. However, this form of treatment requires multiple applications daily for a period of one to two weeks, and a full recovery is dependent upon patient adherence to the treatment regimen.

If left untreated, oral thrush can turn deadly over time. Immunocompromised patients are particularly at risk, as the infection can spread via the bloodstream or upper gastrointestinal tract and lead to more serious conditions like systemic candidiasis which has a mortality rate of 71 to 79 percent.