What can i do to boost my 5 year-old's immune system? it seems like he is always sick with colds and frequently seems run down.

Medical evaluation: First-good medical evaluation - if ok, focus on healthy diet and healthy exercise regimen.

Frequent colds: Children up to age 3 or 4 may normally get frequent colds and upper respiratory viral infections. If a child or adult gets frequent sinus infection or pneumonia, immunoglobulins by blood test should be checked. Low gamma globulin can cause frequent infections. For repeated colds, proper allergy evaluation and treatment, including immunotherapy should be considered. An allergist can help.