Otitis Media
Otitis media is an ear infection that happens when germs get trapped in the space behind the eardrum.
Think of it this way
A small jar has a tight lid. Germs get trapped inside and cannot drain out. They build up and press on the lid from the inside. The jar is like the space behind your eardrum, where trapped germs cause swelling.
Explaining otitis media by grade level
The space behind your eardrum is small and warm. When you get a cold, germs can travel from your nose to that space. The germs get trapped there and make the area swell up. That swelling is what makes your ear hurt so much.