To help relieve your 6-month-old boy from scratching the back of his head to the point of bleeding, one suggestion is to apply mineral oil or olive oil as a protective barrier. It's also recommended to avoid using shampoos for the next few days to prevent further irritation. Additionally, gently combing the affected area after a bath may help. If you continue to have concerns, it may be helpful to reach out to your local pharmacist for personalized advice and guidance.