It is possible that the child may have come into contact with an irritant such as soap, shampoo, new detergent, cream, clothing, bedding, or something else that is causing the skin reaction. It would be best to monitor when the issue started and try using a fragrance-free moisturizing cream to help with the itching. Avoid using harsh soaps in the affected area and gently pat the skin dry instead of rubbing vigorously. It may also be helpful to avoid using the suspected shampoo for now. Consult with a healthcare professional for further guidance if needed.