recurring itchy swollen spot on lower lip, seemingly not food related

30F, yes it itches! I first had it happen last summer, and thought it was a mosquito bite - a spot on my lower lip, at the top of it, basically right on the edge of what you would consider to be inside and outside of the mouth, less than a centimeter in diameter (7mm?) got swollen and itchy, and went away after a few hours. It happened again a couple months later, and I remembered the earlier event vaguely. It started happening more frequently (just started recording it 2 months ago though), roughly once a month for the past 4-5 months. It is always the same spot. It has happened at all times of the day, sometimes after eating, but usually when I haven't yet eaten anything that day. I have tried looking online but have not been able to find anything other than hives, but it seems odd to me that I would just have this one? I mentioned it to my doctor at my physical and got nothing but a "hmm." I'm on no rx meds, take vitamins and probiotics semi-daily. About 2 years ago I had Pityriasis Rosea diagnosed, it lasted for a week or so. About 6 and 3 years ago I had single episodes of my face getting itchy and swollen in random splotches, lasted a few hours and went away. Other current medical issues are digestive - gall bladder problem type symptoms that also started last summer and were occuring monthly, lately more frequently. (I have had various tests for the digestion problems, nothing conclusive yet, gall bladder issue seems most likely). Any insight would be greatly appreciated!!