Natural Dyes and Allergies

A couple of years back I bought some fiber from a shop that uses natural dyes. I carded and spun it and the fiber is beautiful, but spinning it made my hands swell and turn red (irritation, not dye coming off). I’ve put off plying it because of it, though I’m going to ply it probably next weekend (it’s really pretty so I want to finish it, and also I need the bobbins).

I was at Shepherd’s Harvest yesterday and saw so much naturally dyed fiber and I wanted to spin it all, and it’s really pushing me to figure out what it could be about the fiber that I’m sensitive to. Are there certain plants or mordants that can cause this reaction? I’m not allergic to wool or lanolin so I’m thinking it has to be something in the dyeing process.