Swelling from an upper respiratory infection or allergy can block the eustachian tubes, which connect the middle ears to the throat. So air can't reach the middle ear. This creates a vacuum and suction, which pulls fluid and germs from the nose and throat into the middle ear.
The swollen tube prevents this fluid from draining. The fluid is a perfect breeding ground for bacteria or viruses to grow into an ear infection.
Bacterial infections . Bacteria cause most ear infections. The most common types are Streptococcus pneumoniae (also called pneumococcus), Haemophilus influenzae, and Moraxella catarrhalis.
Viral infections. Viruses can also lead to ear infections. The respiratory syncytial virus (RSV) and flu (influenza) virus are the types most frequently found. Inflammation and fluid buildup can occur without infection and cause a feeling of stuffiness in the ears. This is known as otitis media<