My child is 3 yrs and 5 months... he catches cold and cough thrice or sometimes 4 times a month.... specially after he goes out of the house.... may be to school or somewhere else... but when he stays at home, very rare that he catches anything like this... also, he is not a breastfed baby.... his immunity also seems very low.... please suggest some measures to prevent cold and cough and to increase his immunity levels. .. Thank you....