Ear infections most often occur as a result of a viral, fungal or bacterial infection. Most cases of ear infections among children occur after a cold or the flu, and affect the middle ear (otitis media). Infection can also occur as a result of exposure to excess moisture or injury to the outer ear or ear canal (swimmer’s ear). Other factors that may increase the risk of ear infections include:

• Exposure to people with a contagious illness (e.g., cold, the flu)
  
  
• Not being breastfed
  
  
• Exposure to children in day care settings
  
  
• Ear piercings
  
  
• Excess ear wax
  
  
• Foreign objects in the ear canal
  
  
• Injuries to the outer ear
  
  
• Use of irritating chemicals (e.g., hair spray, hair dye) near the ear
  
  
• Lying down while drinking from a baby bottle
  
  
• Use of a pacifier

Young children are more susceptible to ear infections than any age group. Most children in the United States experience one or more ear infections by the time they enter school, with otitis media being diagnosed most often. Many children experience recurring ear infections.

Children are especially vulnerable to ear infections because their immune systems are not fully developed until about age 7. In addition, children have different size structures within the ear, nose and throat that are more likely to lead to pressure and fluid buildup in the middle ear. For example, their eustachian tubes are small and narrow, and are more easily clogged. These tubes are horizontal in young children, so viruses or bacteria can be easily transferred from the nose to the middle ear. The adenoid at the back of upper throat (near the eustachian tubes) is large in children, which can interfere with opening of the tubes and contribute to pressure buildup in the middle ear.