Riboflavin deficiency can cause sores in the mouth (mouth ulcers), cracked red lips, cracks at the corners of the mouth (angular cheilitis), and a sore throat. The eyes may become yellow, stinky and watery, and bright light might hurt the eyes easily so that it is hard to open the eyes in strong daylight (photophobia). A riboflavin deficiency also can cause dry, scaly skin that cracks easily, and itchy, painful private parts.