I had similar concerns about Samantha's ezcema in relation to certain foods. However when I spoke to the doctor about this he said it is very unlikely. Apparently Ezcema is more likely to be seasonal (weather) related than food related.
The only other thing is have you changed washing powders or soaps etc?
I can sympathise. I had thought I had Sam's under control and the last few days it is back with a venegence!
Edited to add: I forgot to say, the doctor also said that a food allergy is more likely to come up as a rash around the mouth or on the tummy and back.
Hope that helps somewhat.
Edited by Mum2Sam