Our Lab Has A Noticeably Swollen Left Jowl. This Was

Our lab has a noticeably swollen left jowl. This was a sudden onset. It doesn't seem to be painful or itch, and I don't see any injury to the area. The swelling isn't far enough back to be a lymph node. I'm wondering if it's an allergic reaction to something. I have Loratadine at home, but don't know if that's safe for dogs... Any suggestions?