When my horses reacted to the Pentosan Gold (last year) it was with a large swelling with edema around the injection site (side of neck in this case). Large meaning about a 10-inch diameter area.
I have since switched back to Wedgewood Pentosan and have not seen any reactions. I also have seen a very noticeable improvement in horse’s movement and comfort, whereas I saw little if any improvement on the HPR Pentosan Gold. Now I question whether the product actually contains any Pentosan at all. Maybe it’s just glucosamine. Who knows what is in there? Good luck finding out.
I’m also wondering, for the people who haven’t had any success with Pentosan, which formula they used.