A yeast infection, also known as candidiasis or thrush, is a common condition caused by an overgrowth of the fungus Candida. This fungus, most frequently Candida albicans, naturally resides in small amounts on the skin, mouth, and gastrointestinal tract. When the body’s environment changes, the yeast can multiply uncontrollably, leading to an infection. Many people search for information about this condition to determine if it is classified as a sexually transmitted infection (STI).
Yeast Infections: Not Technically an STI
Yeast infections are not classified as Sexually Transmitted Infections (STIs) because they are primarily considered an endogenous condition, meaning they originate from organisms already living within the body. The fungus Candida albicans is a normal part of the human microflora. An infection arises when the balance between this yeast and the body’s protective bacteria is disrupted, allowing the yeast to proliferate.
Yeast infections can occur in people who have never been sexually active, including infants, which prevents them from being categorized as an STI. Traditional STIs require external acquisition of a pathogen, but candidiasis results from an imbalance in the existing flora. This distinction is important because yeast infections are not reportable conditions, unlike true STIs such as chlamydia or gonorrhea. While sexual contact can play a role in transmission, the infection’s origin is typically internal.
The Role of Sexual Activity in Transmission
Although not a formal STI, the Candida fungus can be passed between partners during sexual contact. Sexual activity introduces foreign bacteria and can physically disrupt the vaginal environment, which may trigger an overgrowth of yeast. Intercourse can also temporarily alter the vaginal pH, especially through the introduction of alkaline semen, contributing to an environment where Candida can thrive.
Transmission is possible even if one partner is asymptomatic but has an active infection. A male partner may carry the fungus on the penis and transfer it to a female partner, who then develops symptoms. Approximately 15% of men may develop symptoms, such as an itchy rash on the penis, after unprotected intercourse with an infected partner. Because the fungus can be transferred through vaginal, oral, or anal sex, medical professionals often recommend treating both partners if one has a recurrent infection.
Causes Beyond Sexual Contact
The most common triggers for a yeast infection involve factors that upset the body’s internal microbial balance. Antibiotic use is a frequent cause because these medications kill beneficial bacteria, specifically the Lactobacillus species in the vagina, which normally keep Candida growth in check. This reduction in protective bacteria allows the naturally present yeast to multiply rapidly.
Hormonal fluctuations are another common source of imbalance, making yeast infections more likely during pregnancy or when using high-estrogen birth control pills. High blood sugar levels, often seen in individuals with uncontrolled diabetes, provide glucose that encourages yeast growth. Factors that weaken the immune system, such as HIV or certain medications, can also increase the risk of an overgrowth. Lifestyle factors, like wearing tight, non-breathable clothing or remaining in a wet bathing suit, create the warm, moist environment where the fungus thrives.
Recognizing Symptoms and Seeking Treatment
Symptoms of a yeast infection commonly include intense itching and a burning sensation in the affected area. In women, a thick, white, odorless discharge that often resembles cottage cheese is a classic sign of a vaginal yeast infection. Men may experience redness, irritation, or a white discharge under the foreskin or on the head of the penis. Pain during urination or sexual intercourse is also reported by both men and women with candidiasis.
Yeast infection symptoms can closely mimic those of other conditions, including true STIs. It is important to consult a healthcare provider for an accurate diagnosis, especially if this is the first infection or if symptoms do not improve with treatment. Treatment typically involves antifungal medications, which can be applied topically as creams or suppositories, or taken orally as a single dose pill. Preventative steps, such as wearing cotton underwear and avoiding unnecessary antibiotic use, help maintain the body’s natural flora and prevent recurrence.