How do I increase my baby's immune system? He is 6 months old and falls sick at least once a month.

In addition to breast milk, if you are starting solids for your baby, you can make sure he is getting a good mix of vegetables and fruits for the needed vitamins. Also, yogurt or cultured milk drink with probiotic will be good too! A healthy and balanced diet, adequate fluid and rest would help foster a strong immune system.