Wikipedia reports that the eustachian tube links the nasopharynx to the middle ear and is part of the middle ear. When a person is allergic to airborne substances such as pet dander, pollen or dust, her body releases histamines to ward off the allergens, notes Healthline. The histamines cause allergy symptoms, including coughing, sneezing and congestion. Because the eustachian tube connects to the back of the throat, congestion can block the tube, causing problems with the middle ear that result in dizziness. Dizziness resulting from allergies is easily treatable by an internist or allergist.
Sources: healthline.com, en.wikipedia.org