Does it work? Depends. For Candida? I do not know. The one study in the Annals (PubMed) had a grand total of 33 patients and those who had daily ingestion of 8 ounces of yogurt containing Lactobacillus acidophilus had decreased candida colonization and had a threefold decrease in candida vaginitis. Hardly a study with statistical power.
The remaining literature is even more dismal: small numbers that suggest a possible, perhaps, maybe, could be an effect on bacterial vaginosis and H. pylori. Problem is, the strain of lactobacillus found in humans is not the strain found in yogurt (PubMed) and one fatal case in an immunoincompetent patient. So. When you put a patient on antibiotics, will yogurt be of benefit? No good data to support the practice, and the biologic plausibility is suspect. Bon appetite.
For prevention of antibiotic associated diarrhea? Maybe the preferred form of probiotic.