How much could my son's hearing affected by his very bad double ear infection?

Double aar infection: Most of the times the ear infections do not perm. Affect hearing.The effusion does not allow drum to move well& so heairng is impaired if his ear drums are ruptured, his hearing may be affected until his drums heal. If on the other hand he has chronic or recurrent ear infections, you should see his doctor so his hearing can be tested or he be referred to an ENT docotr for that.

Transient: Most middle ear infections will reduce hearing due to fluid trapped in the middle ear space. That reduction is about 40% and disappears when the infection & fluid have cleared. Antibiotics will usually kill the germs within 7-10 days but the fluid may persist for a few weeks. Many docs will suggest an ear recheck a few weeks after completing treatment.