I saw your post today as I was frantically looking for answers on why my 4 year old daughter had this horrible condition all the sudden.
I found out hers is due to OXYCLEAN. I do hope that this might help you in your search. Her skin is sensitive and I even did a test on myself in my inner forearm, it did the exact same thing to me.
She is on antibiotics because of the blisters and to help prevent an infection.
Please let me know if this helps...take care and happy parenting
Be Blessed,Nicole