Some people react poorly to a wide spectrum of foods such as all fermentation products.  Fermentation products include, buttermilk, vinegar, soy sauce, miso, tempeh, tea leaves, coffee, alcohol, yogurt and aged cheese.  Others react poorly to any trace of mold or yeast.  Products that can contain mold or yeast are numerous and include the fermentation products mentioned above as well as sprouts, fruit, fruit juices, nuts, coffee, citric acid, catsup, vanilla extract, any foods enriched with vitamins including enriched flour (the vitamins are often derived from yeast), malted products, sour cream, etc.  Because molds and yeasts are also in the air, the best one can hope for is to keep exposure from ingestion and inhalation very low.