I have a 7 month old Lab mix that started to limp about 2 months ago. We initially took him to the vet for a rash and was informed that he was allergic to fleas. We were given Advantage to use on him as well as LyTar shampoo to help clear up his skin. The next day he started to limp so we took him back to the vet. X-rays were taken and showed up negative for any type of injury. We made him rest and periodically gave him aspirin. A month ago when it was time for his medicine, I again gave him a bath with the special medicine and put on the Advantage. Within a couple of days he started to limp again with the same hind leg. I thought that the Advantage might be doing it. 2 weeks ago on Friday I gave him a bath with the LyTar shampoo before I left for the weekend. When I returned On the following Monday he was limping on his front foot. During the past week that has changed to him limping on his hind foot again. Every time he gets the limp he also stops eating. Any suggestions on something I should have him checked for?????