yeah i had that wen i was 9 ithink and my doctor sed it was cuz when you take a bubblebath and u use that stuff to make bubbles ..... to cure it to take baths and put Arm&Hammer baking soda in the water(:.
They did a urinalysis, which can detect blood in the urine, even if you can't see it. Causes can be minor to major depending on the trace amount. Inflammation, injury, etc. I would check with your medical provider with a more through exam :)