Certain things can make your child more susceptible to ear infections:
Heredity: This explains about 60-70% of the ear infection risk. A history of ear infections in a parent or sibling means there’s a high likelihood of similar problems in other children in the family. Your family may have a structure similarly that makes it more difficult to get ear infections. Boys also tend to get more infections than girls. Being of Native American or Eskimo descent is also risk factor.
Bottle-feeding: Those who drink while lying down or who fall asleep with their bottles are also at risk, since milk can drain through the Eustachian tube and into the middle ear, where it can become a perfect medium for bacteria. You can reduce the chance of infection by holding your baby upright when you feed him. Keep him upright for at least 30 minutes after a feeding to allow the stomach contents to empty.
Pacifiers: Sucking on a pacifier, especially in the daytime, increases the likelihood of a middle-ear infection in children 2 years and older. Some experts believe the constant sucking motion may pull fluid out from the nose and throat and into the middle ear. Pacifiers can also be carriers for germs, so if your child has already had several ear infections, you may want to limit or wean him off the paci.
Environmental Factors: Children who breathe secondhand tobacco smoke are more likely to have ear infections. Smoke irritates the Eustachian tube and paralyzes the hair-like filaments called cilia that line the breathing passages and sweep away germs. When cilia aren’t working, bacteria, viruses and secretions become trapped throughout the breathing passages. Children who regularly play indoors with others, either in daycare or preschool, are also more susceptible to ear infections since they are exposed to more colds and viruses.
Pets: Any allergen in the air can trigger secretions that build up in the middle ear and lead to infection. Animal dander is a common allergen, so keep pets out of baby’s bedroom. If you live in close quarters, an air purifier may help.
Food: In a few cases, an allergy or intolerance to cow's milk and dairy products can also be a factor. An allergy to a food will illicit an immune response, like a tingling mouth, hives or swelling of the lips, even in the smallest amount. A dairy intolerance may cause nausea, bloating, cramping, or diarrhea because of an inability to digest lactose products. If you suspect your child has an allergy or intolerance, consult with your doctor and try eliminating all dairy products from his diet for a short time, then monitor closely for any signs of improvement.
Age: Generally, the younger the child, the greater the likelihood of ear infections. In addition, infants are more prone to infection due to their less mature immune system and floppy Eustachian tube. The younger a child is at the onset of his first ear infection, the higher his chance of coming down with repeated bouts. Fortunately, the risk tends to subside at around age 4, probably because the Eustachian tube lengthens, stiffens, and becomes more vertical, making it harder for bacteria-laden fluid to back up.