What are the best childrens vitamins to boost a 4 yr olds weak immune system?

They don't: The regular diet of a kid in this country cannot escape the built in supplements in store brought foods to the point that vitamin deficiency is rare.If not deficient, vitamins do not help.If your kid has a chronic intestinal disorder with absorption problems, your physician will prescribe the needed products. If vitamins would make you more comfortable, select whatever one the kid will take.

No magic pill: Many people are looking for some "magic pill" to "boost their immune system". There is no such pill. However, there is a way to boost your immune system, live a healthy lifestyle. Proper diet, proper sleep- wake cycles, healthy environment, proper exercise are the foundation of good health and good immune health. Supplements should be used selectively to supplement a healthy diet.

Your pediatrician : Can order labs to determine if your child has an immunodeficiency. If so, a referral to an allergist-immunologist is in order. Healthy children who attend preschool can catch upper respiratory infections often, so the pediatrician will want to know the types of infections , their severity, duration & complications. Keep a journal of the pattern of illnesses & take it with you to the appointment.