Toddler swollen neck(I'm very nervous so please...)

So my 21 month old has several food allergies and we, for the most part, remain away from them. For the last almost month he has had a swollen neck, almost like a mini tire roll around his neck. We took him to the ENT doctor and she said everything looked good. We took him to his pediatrician twice, and the same. We took him to the allergist and he didn't believe it had anything to do with allergies. He also told me a story of a mom who brought her son in because he had a peanut allergy and had a reaction when fed peas. My son also has a peanut allergy and I had been feeding him peas at least 1 to 2 tomes a week at that point. He's able to breathe, thank God, but when I gave him broccoli today the front of his neck swelled up a bit more. His father also gave him a piece of banana so I'm not 100%which it could've been. He's still breastfed and only has a very limited amount of food that he eats. His tongue would swell with bananas but since the allergist wasn't concerned, I wanted to try it again so a few days prior to his neck swelling, we were feeding it to him for a few days. I also believe he has a pollen allergy since he gets so uncomfortable on days with high pollen,rubbing his nose and eyes,scratching the back of his head like crazy. On a regular day, he eats his wheat-free bread about twice which contains about 220mg in sodium. And we also have given him Pedialyte here and there for the last few weeks. I'm writing all of this in hopes to find moms that have any experience with this and if you could share that would be so appreciated right now. I AM SO NERVOUS but am getting over postpartum anxiety/ocd so I'm trying not to drive my family crazy since I've done enough of that in the last few months.

He has a chunky face so it looks like it'd naturally be a chunkster roll, but it's not unfortunately. Looking at it from the front is not as subtle as the side view but he's giving me a hard time so...