My three year old son had pinworms , so two weeks ago we treated it with the over the counter meds we found. Since then he has had four bowel movements that included a small amount of blood . Not dark, very bright red blood and twice it was very little but twice it was about the size of half a dime of blood. He has started complaining again of itching and waking last night, I need to do his second dose today, however, should I be concerned with the blood in his stool? He has had hard stools and says it hurts to pass them, those were the only times he bled. When he had soft stools, no pain, no bleeding . Just wondering if this is a side effect of the pinworms or meds??