Oral consumption of yogurt does not usually produce side effects in healthy adults, although illness can result if the yogurt is contaminated with harmful forms of bacteria, explains WebMD. In rare cases, live bacteria naturally found in yogurt can reproduce uncontrollably and cause disease in individuals with weakened immune systems.
To minimize the chances of falling ill from eating yogurt contaminated with disease-causing types of bacteria, it is important to eat only yogurt that is stored and prepared appropriately, advises WebMD.
Lactobacillus is a form of bacteria found naturally in yogurt that also exists in the human digestive and urinary systems, usually without posing any health threats, notes MedlinePlus. Rather, this form of bacteria is often beneficial to health and has uses in the treatment of a wide variety of conditions, such as diarrhea, urinary tract infections and general digestive issues. Lactobacillus has the potential to cause disease in individuals with compromised immune systems, such as those who have received organ transplants and HIV or AIDS patients. Such individuals should avoid consuming yogurt in large amounts unless advised otherwise by a health care provider, according to WebMD.
Women sometimes use yogurt vaginally to treat yeast infections, notes WebMD. As of January 2015, there is insufficient information available on the safety of using yogurt vaginally while breastfeeding. For this reason, nursing women should refrain from using yogurt intravaginally until researchers investigate the topic further.