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Allergy-induced dizziness can be caused by allergens.
If you’re allergic to certain airborne substances, including dust, pollen, and pet dander, your body begins releasing chemicals including histamine to fight off these perceived intruders. These chemicals are the cause of what you know of as allergy symptoms.
Typical allergy symptoms include:
sinus congestion
sneezing
itchy throat
postnasal drip
coughing
Allergies can affect the Eustachian tube. This tube is essentially a tunnel that connects your middle ear to the back of your throat and helps to regulate your balance, while also equalizing the pressure in your middle ear with the ambient air pressure.
When you begin experiencing symptoms in your ears, including that annoying clogged feeling that can make it difficult to hear, it’s often because your Eustachian tube is blocked with mucus.
When it’s blocked, it’s no longer able to equalize pressure in the ear and maintain balance in your body.
These middle-ear disturbances can cause symptoms of dizziness in people with allergies, colds, and sinus infections.
Healthline.com