Yogurt remains safe to eat unrefrigerated for 4 to 6 hours. The processes used to create this dairy product increase the acidity of milk which also helps to prevent spoilage.
Mold is the primary threat to unrefrigerated yogurt. As it grows, mold lowers the acidity of the product allowing pathogens to grow.
Yogurt is an important source of nutrients and live cultures that aid in a healthy digestive system. The manufacturer introduces live helpful bacteria into milk and holds the product at a temperature to encourage their growth. As the milk ferments it curdles, forming a thick and tangy product. Refrigeration prolongs storage times for the finished product.