This same 'warning' was already mentioned in another THREAD which I made a lengthy reply to based on our hospital's experience with it since last fall and the recent seminar I went to regarding this product. Someone also added to that their positive experience with the product on their boxer.

It's not a good thing to use email or a few oft quoted experience of one person, or even two people, as a basis for your judgement on anything. If you have questions on a product ask your vet, research reputable animal health sites (ahaa, javma, avma, cornell, etc), and find the product inserts online whenever possible for more complete information.

Emails or quotes from one person's bad experience out of thousands, or tens of thousands does not mean the product is to be avoided at all costs for everyone.

For all we know the person did not apply the product correctly (which is my guess) or follow the directions properly, or the person could be a rare person that is highly allergic to certain things that the vast majority of the population is not. The quoted bad experience is a one sided story and should be taken with a grain of salt unless other reputable/verified information is found.