I think that many peptide sites say this since peptides land in the legal gray area, thus statements like, "for research purposes only". Funny thing is our dog has had joint problems since birth, so I looked into using peptides for her. I didn't find a damn thing on using peptides for dogs anywhere. Admittedly, I did't exhaustively research the subject, digging past page two of the google search, but it was interesting to come up empty handed. Nevertheless, its not a bad thing to have a little healthy paranoia when it comes to injecting things into your body...