Are you sure that it is cradle cap and not psoriasis or eczema? My youngest son had bad cradle cap as a baby and after I got rid of it, it appeared to be coming back. It was really psoriasis which manifests itself in scaly whitish or yellowish patches, sometimes with red margins. My son still gets patches of psoriasis from the size of a pencil eraser up to the size of a half-dollar coin on his scalp and body. Vit D ointment and tea tree oil help to get rid of them, as does a gentle abrasive to slough the scales away.