Canned sardines present two potential triggers for eczema management. The first is histamine accumulation from processing and storage — the same scombroid issue as tuna, though sardines typically have somewhat lower histamine levels on average. The second is parvalbumin, the protein responsible for most true fish allergies, which sardines contain at intermediate levels.

Sardines also create a clinical tension because they are rich in omega-3 fatty acids (EPA and DHA) with documented anti-inflammatory benefits for eczema — eliminating them removes both a potential trigger and a potential treatment. A useful diagnostic clue: if canned sardines trigger a reaction but fresh sardines do not, histamine rather than the fish protein itself is the more likely cause.