My 10 months son has has 3 ear infections in the last 6 weeks and has had 3 courses of antibiotics. what could be the cause?

Many issues: The fluid behind the eardrum will often not clear for 4-6 weeks after an initial germ is killed by treatment and will remain as a tempting source of food for any other germ in the babies throat.Primary treatment may have failed, or reinfection may have occurred in each instance. If a kid goes 90 days without clearing they will often need tubes.