What Causes Swollen Area Under The Lips?

I woke up this morning with a 1 inch size area of tissue between my lower lip and the point of my chin, that has thickened and swollen up about 1/4 inch. It is not painful but it is uncomfortable and definitely unattractive. It is the same symptoms as similar recent episodes where some portion of my lips swell up, but this is the first time it has affected my chin. The symptoms usually last about a day and then shrink and disappear. I am a 55-year old white male, in good health overall. The swelling episodes first happened a few times when I was 19 but disappeared until this year. Now I am getting them about once a week. I have tried to identify a food or other source of allergen, but have not had any luck. Any suggestions for how to narrow it down?