Many ask: How Long After I Eliminate a Food From my Diet Will it Take to be Out of my System? Typically three days and the food will be gone but the irritation caused by the offending foods may take weeks to resolve to a point where symptoms will no longer be felt. Symptoms that are shown such as eczema may take longer to resolve. After years of abusing the body with something it didn’t like, symptoms do not all disappear overnight. However, there will be a significant and immediate improvement for most that have always experienced immediate symptoms after ingesting an offending food.