When we lived in a hard water area, adding a chelator was an absolute game-changer to get rid of soap scum, and eliminate that sticky, itchy feeling on my hands. Even though we have a whole-house filter now, I still use a chelator because I never know if my users will have hard water. I don't want them to hate hand-crafted soap just because of their water!
Fortunately, my super sensitive skin does not react to either citric acid or sodium citrate. Although I already have citric acid around for bath bombs, I went ahead and bought sodium citrate, because no lye adjustment is needed and it's relatively inexpensive given how little I use (1% for most soaps, and 2% for high-lard or high-tallow recipes, which tend to create more scum).
My understanding is that most citric acid these days is often fermented on a corn substrate. Sodium citrate is made from that citric acid, too. Supposedly there is no corn left in the CA, just as there is allegedly no corn or beets left in the sugar manufactured from those. But if you are sensitive to corn, I'd purchase only a small amount of either to try as your chelator.
EDIT: are you already using sodium lactate or white sugar in your soap without any problem? If so, given that those are both created from corn or beets, you might be ok with citric acid or sodium citrate, too.