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When the prof suggested natural yoghurt I thought the same, that it would have to be applied rather than eaten so I asked. He laughed and said eaten. Apparently the application method is good for thrush, not cystitiis. However, as I said I am willing to try anything so I might do both. Actually, I would find applying it easier, because I wouldn't have to taste it. The answer by ethandron had the suggestion of a book, so I shall probably buy that as well. Every little helps! Thanks a lot everyone.