The major cause of yeast infections is an overgrowth of the fungus Candida. Candida is a naturally occurring microorganism found on the skin and mucous membranes, but when it multiplies uncontrollably, it can lead to infection. Factors contributing to Candida overgrowth include a weakened immune system, hormonal imbalances, antibiotic use, and poor nutrition. Understanding the etiology of yeast infections is essential for developing targeted treatment strategies.