Some people seem to feel an allergy can be involved. Sassy used to need to have her sacs expressed once a month or so. When I changed kibbles she would be fine for several months each time. Strange, I wasn't going to different proteins or starches or anything. When she went on home cooked food due to a health problem she mostly stopped needing them expressed. In the two years she has been eating home cooked food she both stinks less and has needed those sacs expressed only three times. I think the canned plain pumpkin she always gets helps as well. Many dogs love it, try a couple tablespoons mixed in the kibble.