I went looking for info on this topic and found this thread. I wanted to start collar conditioning w/my 8 mo old YLM so I put the collar on him to get him accustomed to it. I left it on for about a week, 24/7 when I noticed the sores. I never even turned it on. It's definitely possible I had it on too loose, I was using the "2 finger" rule. I also wondered about an allergic reaction as this pup does seem to have sensitive skin. I think I'll try again and tighten it up and shorten the period of wear. If that doesn't work, I'll look into the alternate contacts. Thank for the info!