Understanding Yeast Infection - the Basics

What Are Yeast Infections?

Yeast infections -- sometimes called candidiasis -- take many forms. They often develop where a moist environment encourages fungal growth, especially in the mouth, on the webs of fingers and toes, genitals, nails, and folds of skin.  Types of yeast infection include:

• Oral thrush is a painless, often recurrent yeast infection of the mouth and throat.  It is common in babies, young children, and the elderly, but can affect people of all ages.
• Moniliasis is a vaginal yeast infection experienced by about 75% of women, most commonly during pregnancy or treatment with antibiotics.
• Balanitis is a less common but equally irritating infection of the penis. 
• Intertrigo occurs on the skin, particularly in large skin folds in obese people.
• Systemic yeast infections can occur in people with diabetes, AIDS, and other conditions, or people taking drug treatments that suppress the immune system.

What Causes Yeast Infections?

Candida albicans is a fungal organism, or yeast, that thrives in your mouth, gastrointestinal tract, and skin. Your body normally produces bacteria that keep this fungus in check.  But when fungal growth exceeds the body's ability to control it, yeast infection develops. This can happen when you're weakened by illness or upset by stress.  Antibiotics that treat many conditions can also kill the bacteria that otherwise control fungal outbreaks.

Yeast infections are common among dishwashers and people whose hands are often in water, in children who suck their thumbs or fingers, and in people whose clothing retains body moisture.  The diaper rash called candidal dermatitis is caused by yeast growth in the folds of a baby's skin.

Diabetics are especially prone to yeast infections because they have high levels of sugar in their blood and urine, and a low resistance to infection -- conditions that encourage yeast growth.

In rare cases, the candida fungus may invade the bloodstream through an intravenous (IV) tube or urinary catheter used during hospitalization.  If the infection travels to the kidneys, lungs, brain, or other organs, it can cause serious systemic complications, but these usually develop only in people who are seriously ill or who have other health problems that weaken the immune system, such as drug addiction or diabetes.