There is actually very little written on this, and I’ve scoured both the web and Pubmed. Thus far, the biggest culprit ingredient linked to eczema, asthma and allergies is Sodium benzoate. This has been covered last week where sodium benzoate is a preservative found in soft drinks, and linked to allergy and behavourial issues.
I only found one study on Pubmed, where 62 children from age 12 months to 13 years were observed for whether restriction in their diet led to an improvement in eczema. Among the restricted foods, soda (11.9%) was the highest, followed in decreasing order by food additives (9.2%), walnut (7.0%), peanut (7.0%), and other nuts (5.9%). When foods were grouped, the crustacean group was the most frequently restricted group, followed by processed foods, nuts, milk & dairy products, and meats.
The observation from the study was that atopic dermatitis/eczema improved for those children which had restricted 1 to 3 food groups, and those that avoided more than 3 groups didn’t showed significant improvement. There may therefore be some impact on restricting foods, but it is not clear nor a causal link directly established through this study.
There are many websites though, through personal testimonies, where various individuals found that removing sugar, caffeine, preservatives and artificial sweeteners from their diets helped. In this case, as there is little nutritional benefit of such ingredients for our children, restricting these ingredients from their diet should be a plus (if not for eczema, for healthy living!).