Hi Fever is a sign of infection. If he never required antibiotic, most likely that they were all viral in origin. Usually viral fevers are associated with running nose/ cough/ red watery eyes etc along with fever. And Viral fevers may precipitate allergy. And it is common for all kids under 5 yrs of age to have 6 to 7 episodes of upper respiratory infections in a year. But if each and every episode resulted in a chesty cough or wheeze or breathing difficulty resulting in a prolonged illness, then it means he has Allergic Bronchitis. If this is the case, there are preventive medications and your Pediatrician will help you with this. Generally to prevent infections, hand hygiene, food and water hygiene are important. You might give him multivitamin/ zinc/ iron supplements after consultation with your Pediatrician as these micro nutrient deficiencies if present, can make your baby more prone to infections. And as a last note if the fever episodes were not associated with any other symptoms, I would suggest that his urine is checked to rule out Urinary Tract Infection. Hope my answer helps you. Wish your son good health.