Vinegar triggers eczema primarily through its histamine content, which is produced during the fermentation process. The type of vinegar matters enormously: red wine vinegar has the highest histamine (up to 4,000 µg/L), followed by balsamic, then sherry vinegar, then apple cider vinegar, with white distilled vinegar having the least.

For the roughly one third of people with eczema who have reduced ability to break down histamine, vinegar can be a significant trigger — and it is particularly difficult to avoid because it hides in so many everyday foods. Salad dressings, ketchup, mustard, mayonnaise, marinades, hot sauces, pickles, and sushi rice all contain vinegar, making cumulative daily exposure high even when individual servings seem small.