What could cause bloody diarrhea in an infant with no symptoms?

Never Normal. Bloody bowel movements are never a normal event. The color of the blood sometimes gives you clues from where the blood comes from, the brighter the closer to the rectum and colon, the darker the higher in the g.I tract . It can be anything from a fissure in the anal opening due to hard stools, an infection, if your child has been in antibiotics, an allergy to milk, to bowel problems. Dr asap.