http://www.quackwatch.com/01QuackeryRelatedTopics/candida.html
Long and short of it, the only "real" cases were from people who read a book about this issue and came in saying they had this problem.
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Quote from the article:
In 1986, two doctors from Loyola University Stritch School of Medicine reported seeing four young women whose nonspecific complaints included chronic fatigue, anxiety, and depression. All four mistakenly believed they had disseminated candidiasis and were taking nystatin or ketoconazole, which had been prescribed by their family physicians. All had read The Yeast Connection and had carried the book into the office during their visits. One patient on ketoconazole had hepatitis, which resolved when the drug was stopped [9].
Worse yet, a case has been reported of a child with a severe case of disseminated candidiasis who had been seen by a "Candida doctor" and given inadequate treatment. The report concluded that "the advice of yeast connection advocates may be inappropriate even for illnesses in which Candida is implicated." [10]
Perhaps the saddest report was a letter in a health-food magazine from a woman appealing for help and encouragement. She said that a clinical ecologist had been treating her for allergies and Candida for four years, that initial tests showed she "was allergic to all foods" as well as to numerous chemicals and inhalants, and that so far nothing had helped.
End quote.
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The self-diagnosis is hilarious if not scary. "Abdominal pain? Mood swings? Craving for bread, sweets and alcohol? Ever had birth control?" Wow, that must be a yeast allergy! Get to the doctor! Oh wait, no, that is my wife once a month.
It does indeed seem fishy. If this really is a good buddy of yours, talk to him about how this might be a really bad prognosis, and he should see a doctor from a real medical facility if he is instead seeing some form of "specialist" or someone with a private practice. The biggest fear is that he has some other illness or condition that is being ignored because of some "doctor" saying he has a yeast allergy. Research says there is really no such thing.