How can I boost my childs immune system (frequently sick!?!)?

maybe her immune system is weak.. get a second opinion from another pediatrician because it sounds like she gets sick a lot!! Aslo, was she fed and do you share custody? if so, what does she eat when with her father? or anyone else for that matter.. mixing way heathly food with way unhealthy food could be a factor as well... i would read books on how to boost your childs immune system, you will find them helpful i think