Hi,
    Thanks for the query . I understand your concern.
    The recurrent symptoms  you child has can be attributed to allergy . He needs assessment of allergens ( the 
substance causing allergy ) & management  to avoid exposure to them.
   *   Allergens could be detected by -
         - Observation for possible triggering  factor that came in contact ( dust, fumes, smoke, talcum powder, scent/ certain  edibles( mostly of protein group), certain vegetable, fruit / clothes used etc )
          - It can be identified by allergy screening test. 
   * Prevention- It's by preventing exposure to allergen,
                     - Desensitization treatment.
                     - by using 
Histamine blockers 
     You need to consult a chest physician( 
pediatrician ) for this.
   * Use of 
vitamins A, C, D for building resistance as per treating doctor's advise .
     Thanks