Similary as explained above, my 5 year old Boxer just did this last night for the first time. I read everyone's posts and I realized that for the last 2 months we have been giving out dog Advantage. We used to give it to him as a puppy and stopped because he never got fleas again. 2 months ago we noticed them so started him on Advantage. I see that Frontline may be a culprit, but I'd like to know what others find out.