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Oral Thrush – Causes, Symptoms and Treatment

Thrush, also called oral candidiasis, oropharyngeal candidiasis or moniliasis, is a type of mouth infection caused by an overgrowth of the Candida fungus, commonly known as yeast. It can affect the corners of the mouth, insides of cheeks, palate, tongue and throat. Thrush most often occurs in individuals with compromised immune systems, such as patients with HIV/AIDS or cancer, those with uncontrolled diabetes and in children under the age of six months.

Risk Factors and Causes of Thrush

An overgrowth of a yeast called Candida albicans is the cause of the majority of thrush infections. Small amounts of these fungi can be found in the mouth, skin and digestive tract. In most cases, the body’s microflora prevents these fungi from multiplying. However, sometimes yeast can grow uncontrolled and cause thrush. This happens when certain factors, such as diseases, medications or high blood glucose levels alter the environment inside the mouth or throat. In addition, people with compromised immune systems lose the ability to fight off potentially harmful microorganisms in the body, putting them at higher risk for thrush. Thrush also affects babies and is very common in infants under six months of age.

Hence, factors that may make a person more susceptible to thrush infection include:

  • Compromised immune system due to chronic diseases as well as the underdeveloped immunity in infants or declining immunity in the elderly.
  • Cancer itself and cancer treatments weaken the immune system, increasing the risk of thrush infection.
  • Poorly controlled diabetes mellitus can cause sugar levels in the saliva to increase, contributing to the growth of thrush.
  • Use of certain types of medications, including chemotherapy drugs, corticosteroids, antibiotics, birth control pills and drugs that suppress the immune system.
  • The HIV virus damages the cells of the immune system, which makes the person more vulnerable to infections such as thrush.
  • Dry mouth which occurs when the saliva glands fail to produce adequate moisture in the mouth, thus disrupting the balance of microorganisms in the mouth.
  • Vaginal yeast infections which happen to be caused by the same fungus that causes thrush.
  • Pregnancy can also increase the risk of thrush because the higher levels of female hormones alter the balance of bacteria in the woman’s mouth and vagina.
  • Vitamin deficiencies and/or malnutrition.
  • High sugar diet.
  • Certain oral practices such as poorly fitting dentures or the overuse of antiseptic mouthwashes can increase a person’s risk of developing thrush.
  • Poor general health.

Thrush is rarely passed from person to person through casual contact. However, it can be transmitted during a vaginal delivery or through breastfeeding if the mother has a yeast infection. Older children and adults usually develop thrush due to various factors listed above which can promote overgrowth of the Candida fungus.

Symptoms of Thrush

For most people the first signs of thrush are bad taste in the mouth and decreased taste sensation. White, creamy lesions that resemble cottage cheese often develop inside the mouth and usually affect the tongue, palate and corners of the mouth (but they may also occur on the gums, tonsils and lips). In addition, the corners of the mouth may become cracked, red and moist.

In most cases, thrush is initially painless. However, as time goes on, especially if infection has spread from the mouth to the palate or throat, many people start feeling discomfort in their mouth. In severe cases, lesions may spread into the esophagus, triggering a serious condition called Candida esophagitis. When this happens, most patients will experience pain or difficulty swallowing, sensation of food sticking in the throat or the chest and sometimes also fever.

In infants, thrush is often mistaken for milk on the tongue or inner cheeks. Babies with thrush sometimes experience diaper rash as the infection spreads through their digestive tract. Nursing babies may pass thrush on to their mothers by infecting the nipple during breastfeeding. An infected nipple can be red, cracked and sore and the skin of the areola can be tightly stretched and shiny.

Diagnosing Thrush

Given its distinct appearance, a doctor can usually diagnose thrush by looking for the characteristic white lesions on the mouth, cheeks and tongue. When the doctor gently brushes away these patches, they will reveal tender, reddened areas that may bleed lightly.

Doctors unable to visually confirm the presence of thrush may use a KOH prep test (a microscopic examination of scrapings from the mouth). In rare cases, a biopsy may be necessary. Patients with persistent thrush infections may need to be checked for other conditions that may be contributing to thrush, such as undiagnosed diabetes, HIV infection or cancer.

If thrush has spread to the esophagus, causing serious complications such as Candida esophagitis, additional exams may be ordered, including:

  • Throat culture. The micro-organisms from the tissue sample taken from the back of the throat are studied under a microscope.
  • Endoscopy of the esophagus, stomach and the small intestine with the use of a flexible camera that captures images of the lining of the esophagus and surrounding areas.

Treatment of Thrush

In most cases, thrush responds well to treatment and is not considered to be a serious medical condition. Mild thrush can be easily treated with simple home remedies. For instance, consuming unflavored yogurt containing live cultures or acidophilus capsules as an alternative to yogurt can help many patients cure the infection. Warm saltwater rinses or baking soda rinse can also be effective. Mild cases of thrush may disappear within 24 to 48 hours of treatment.

Moderate to severe cases of thrush can be treated successfully with antifungal medications, which inhibit the growth of yeast. These include antifungal lozenges or mouthwashes as well as oral antifungal medication for more severe infections.

Failure to adequately treat thrush in nursing mothers and their babies may result in the mother and child repeatedly infecting each other during breastfeeding. Infants are typically treated with topical antifungals when medication is necessary. An antifungal cream may be prescribed to treat mother’s breasts and associated diaper rash in babies.

People with severely compromised immune systems and recurrent thrush infections, e.g. those with HIV or AIDS, may notice diminished effectiveness of antifungal medications over time and may need to be prescribed a medication called amphotericin B when all other treatments have failed.

Left untreated, thrush may not only become persistent and painful but it can also spread to the gastrointestinal tract, respiratory tract, liver and skin. In rare instances, invasive candidiasis characterized by infections in the organs and bloodstream may occur. This condition may affect the following organs:

  • Heart (endocarditis)
  • Brain (meningitis)
  • Eyes (endophthalmitis)
  • Joints (arthritis)

Preventing Thrush

Thrush may be often difficult to prevent completely because the Candida fungus is so common. However, individuals at increased risk of developing thrush can reduce the likelihood of infection by using antibiotics only as prescribed by their doctor and eating unflavored yogurt or acidophilus capsules when taking antibiotics. Other tips include avoiding mouthwashes or sprays, seeing the dentist at least twice a year, brushing and flossing regularly, keeping dentures clean and reporting any mouth irritation or soreness promptly to the dentist. In addition, patients with diabetes can help prevent thrush infections by controlling their blood glucose levels.