An allergy to peanut butter is probably caused by an allergy to peanuts. Such allergies are the immune system's overreaction to harmless substances. Instead of letting you enjoy peanut butter, your body attacks the proteins in peanuts by releasing antibodies called immunoglobulin E. The antibodies then release chemicals, including histamine, to kill off the invading peanut allergen. Your body responds to these chemicals with a variety of allergic symptoms. These symptoms can include skin problems, respiratory issues, stomach disturbances and worse.
Research has shown that there might be a link between food allergies -- peanut allergies included -- and middle ear infections. Middle ear infections are the type that kids commonly get, where fluid is trapped behind the eardrum and bacteria grow, causing an earache. They usually go away on their own, though doctors can prescribe antibiotics, too. Inner ear infections are less understood; they typically cause intense vertigo. There's no evidence so far that allergies can cause an inner ear infection.
If you have an allergic reaction to peanuts, the tube that connects your throat to your ear might swell up. The swollen tube then causes fluids, which belong in your throat, to get trapped behind your eardrum. Those fluids contain bacteria, and the warm, dark inner ear is a good spot for the bacteria to keep growing. The bacteria then cause an ear infection called otitis media with effusion, which is noticeable by symptoms that include a fever, cough, runny nose and ear pain. Studies point out that antihistamines could prevent the swelling of the tubes and thereby prevent allergy-related ear infections. It's important to note that in general, ear infections aren't caused by allergies; the research has uncovered a link that's applicable in some cases.