My son had lots of ear infections under 3 years old and we were told it was possibly causing glue ear. He didn't need grommets and it did stop of it's own accord. However, it left him with a dislike of loud noises and the doctor said this is because his hearing would have been affected, and now that the glue ear has cleared, sounds suddenly seem really loud to him. Apparently, this problem resolves in time as kids get used to the new volume of sounds!
I found this site was good for info on glue ear:
http://www.nhs.uk/conditions/glue-ear/Pages/Introduction.aspx
This has good info on ear infections:
http://www.nhs.uk/conditions/otitis-media/pages/introduction.aspx
This is good info on Perforated eardrum which can be caused by ear infections.
http://www.nhs.uk/conditions/perforated-eardrum/pages/causes.aspx