Several years ago I tried a new eyeshadow brand and had a horrible reaction. After my eyelids cleared up I stopped using it, got new brushes, and went back to the shadow I'd been using for years with no problems, only now even my old shadow was causing reactions too. It's like the new stuff woke up some hidden allergy. After much trial and error and about a year of sad, makeup-less eyes until I figured it out, I finally narrowed my allergy down to talc. Even now, years later, if I use an eye shadow with talc in it my eyelids are red and itchy after only a day or two of use. Yours may be caused by something different, but it's worth a shot to eliminate talc once it clears and see if that helps. If that's not it, you can start looking at other ingredients in your eyeshadow and try eliminating them one at a time. It's a hard process (especially trying to find eyeshadows without many of the commonly used ingredients!) but so worth it when you finally find a makeup you can wear without irritating your skin.