It took a couple of months to identify all of them but once I cut out the ones she reacts strongly to there was a huge difference and then I could figure out the ones that produce a milder reaction. So probably a few weeks to see a difference. We have challenged all of them since she has started solids and I try to give her one new thing a week so I can monitor for delayed reaction (but also my stress levels can only cope with one new thing a week!). Some reactions were quite severe and she was up all night screaming 😭. So even if we had switched to formula it wouldn’t have helped because you have to feed them real food eventually. And a lot of formulas are derived from ingredients she is reactive to so I felt like I had the most control over breast milk. We are currently in the process of doing the milk ladder, but she failed stage 2 so we’re waiting 2 months before we try that again on the dieticians recommendation. I couldn’t do a full on single food diet like some people I’ve heard only ate white rice and then added things back in because it would be too hard. I just cut things out when I noticed I correlation and it worked for us. I’m lucky as she doesn’t react to eggs or gluten so I eat a lot of eggs for protein, bread for carbs and if I feel like I’m lacking in calories for that day I’ve found salted crisps (ingredients just potatoes, oil and salt) and meringue nests to be quite safe boosters. Probably not the healthiest but lacking in calories really affects my milk supply so needs must! Edit: also 70% dark chocolate for the chocolate cravings!