Hi Cheryl
That container was a 4lb container of STPP from Soapgoods. If it's good enough for them to put it in, I figured it was good enough for me to keep it in.
Beth. Something doesn't sound right here! Was the 2 ounces you used, by weight or volume? Either way I can't possibly see how this would cause a allergic reaction. I have heard if allergies to dyes, perfumes, and optical Brightners, but never to STPP. Are you sure you got STPP and not TSP? Did you use a fabric softener, or a dryer sheet? More of a chance to have allergic reaction to those!
The Arm&Hammer liquid is something you've been using so ??
Without doing any math, I'd say that with your water and the number of gallons that goes into the machine for a full load you should need more STPP than the little scoop that come with the OxiClean. It also cause me to wonder if your machine doesn't rinse well, or you over loaded it.
Regardless of all that, if you have someone in the house with sensitive skin in the house, it's always a good idea to do a second rinse.