If your 2 and a half year old child has "cradle cap" on the back of their head, there are a few things you can try. One option is to use a baby shampoo specifically formulated for this issue, such as Bebeginol, which can be found at a pharmacy. This shampoo is usually effective in resolving the problem in young children. If the issue persists after a few weeks of using the shampoo, it would be a good idea to consult a pediatrician for further advice. This condition is typically temporary and tends to resolve on its own.