eczema

I am at my wits end with Eli's eczema. I have no idea what will cause a break out. It seems like they just happen, he just breaks out, sometimes for no apparent reason. When my parents were out after Anna was born they took him to the park one day and when they brought him home his back was all broken out. Ben took him to the park not too long after and no skin change. I was giving him hot dogs the other week with no breakouts, I gave him some hot dog today (same kind) and he's getting little red spots on his arms. I'm so afraid to try new foods because I don't know what will cause a big breakout but apparently it doesn't matter cause he breaks out willy-nilly. Hell, before we started to work milk into his diet (we found the only way to get him to drink some is to mix it in with some formula, hopefully we can successfully up the milk and decrease the formula till he's drinking straight milk) I had him just drinking formula, no table foods, for 2 days so that if the milk caused him to breakout I would know for sure it was the milk and not something else. I ended up having him on formula for more like 3 days and in that time he had a little breakout on his leg, it cleared up with the eczema cream we have but what the hell caused him to break out? GAH I hate eczema. I hate it I hate it I hate it. Ben tells me to be thankful thats the only thing wrong with him and I try. I try really hard to be glad that besides the eczema he is a growing, thriving, happy, beautiful little boy, but my god it's so frustrating!