C.P.
My daughter used to have bad migraines everyday. She went to college and found out that if she does not eat dairy at all then her headaches do not even get started. She could tell almost immediately but it may be different for eczema. I have not asked her about eczema because she had that also. You might want to start you son on a good probiotic from the health food store which cleans the intestinal tract and help to control eczema.