Wow, I was just thinking about this. While some foods do aggravate my eczema when it is already inflamed (lots of dairy, chocolate or coffee), I don't feel that it is due to a food allergy. I think, at least for me, that it has much more to do with hormonal changes. For instance, the first time it got really really bad for me was when I was about 12-13. Then it flared up again badly after the birth of each of my children. I was diagnosed hypothyroid and once that was under control it was better but not great. Last week it flared up unbelievably bad, and then a day later I got my period.
So while I don't know that it's 100% caused by hormonal fluctuations, I think they have a lot to do with it.