I wish I knew the answer but I do have some ideas because I have psoriasis which seems very similar to eczema. There are some foods which I avoid because they seem to make my psoriasis worse. These are not BAD foods. Just foods that my body does not tolerate well.
The foods I tend to avoid are all Nightshades (plants that grow in the night) like potatoes, tomatoes, eggplant, and peppers. So, while it is no guarantee it could be that you might be having a problem with these foods. In my case potatoes would be the first thing for me to suspect. I also have problems with Gluten and so avoid anything with gluten including wheat.
These sensitivities that I have do add some restrictions but I find I can eat all the starchy foods that I need by eating a lot of root vegetables. In particular beats, parsnips, sweet potatoes and yams (yes, they seem ok for me), turnip, rutabega, yuca, taro, boniato (like a white sweet potatoe). I can also eat plenty of whole grains that do not contain gluten such as rice, millet, buckwheat, quinoa and more.
I do not know if this will help but maybe you can try removing nightshades and gluten from your diet and see if the condition clears up some? If it does you can then add some of the foods back, one at a time, and see if the conditions return. If so you have a probable culprit and can test the theory a couple more times to be sure.
I almost was thinking of trying the elimination diet that Dr John McDougall suggests for finding food allergies. This would eliminate wheat, and many other possible sources of allergies as well, including citrus. Just thinking out loud here.
You can really learn a lot by going through a process of elimination. I had to do the same thing to figure out what some of the triggers were for my Psoriasis. I learned quite a bit that way and was able to greatly reduce my symptoms by simply avoiding some of the foods that were causing me problems. Occasionally I will try adding something back in that was previously eliminated. So, the process can be ongoing. We have heard of some people who are sometimes able to eat, at a later time, foods that once caused them problems.
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