Toddler had blood found in stool she's 5 doing more test what can cause this?

Blood in stool: The most common reason a toddler would have blood during stooling is due to the passage of hard, constipated stools. Softening the stool usually resolves this. If her stools are normal, the blood could be a sign of a food allergy. There would also be mucous and episodic loose stools. A more rare cause would be inflammatory bowel disease. Stool & blood tests can distinguish these causes.