When the Israelites were wandering lost in the desert back in the time of Moses, they were fed with a substance that fell from the sky and made a wonderful bread. They called it "manna", which literally means "what is it?" because they had no clue. To this day, we don't know exactly what it was.
Similarly, a short time after "Boo" joined our family, she developed a skin rash on her hands whose cause we could not pinpoint. We tried lotions and creams galore, changed our hand soap and shampoo, to no avail. Finally, we took her to the doctor who was also stumped. He said that if she was a mom he would say she had "dishpan hands", but that made no sense for her. He gave us a prescription strength cream that was a stronger version of something we were already using.
The cream cleared up the problem, but the doctor said it would probably come back since we had not identified the culprit. My theory was that the hand soap or antibiotic hand wash at the school was causing the problem. Since school ended the problem has not come back, which makes me think I was right.