What are Sinuses & What is Their Role in Allergies?

What are Sinuses?

Sinuses, also called paranasal sinuses, are structures located within the bones of the skull — mostly around the nose.

Sinuses are not just empty spaces; they serve important functions within the respiratory system. The walls of your sinuses are lined with a thin layer of mucus that act as a natural air filter. This mucus traps tiny particles like dust, pollen, and other airborne irritants, preventing them from reaching the lungs.

By trapping these particles, sinuses help protect delicate lung tissues from potential damage and contribute to overall respiratory health.

Sinus Anatomy: Where Are the Sinuses Located?

There are four primary types of sinuses each named after the after the bones they are in: the maxillary sinuses, the frontal sinuses, the ethmoid sinuses, and the sphenoid sinuses¹.

The maxillary sinuses are the largest of the sinuses. They're situated on either side of the nose, beneath the cheekbones.

Above the eyebrows, in the forehead, are the frontal sinuses.

The ethmoid sinuses, a group of small sinuses, are located between the eyes, behind the bridge of the nose.

Deep within the skull, behind the eyes, reside the sphenoid sinuses.

All these sinus cavities are linked to the nasal cavity by tiny openings called ostia. These openings allow for mucus drainage from the sinuses into the nose. However, when the ostia become obstructed, mucus can build up in the sinuses, leading to inflammation and discomfort.

What Causes Sinus Pain and Congestion?

Sinus pain and congestion are common symptoms that can significantly impact quality of life. There are several underlying causes of these discomforts, ranging from infections to allergies.

One common cause of sinus pain and congestion is a sinus infection, also known as sinusitis. This occurs when the sinuses become inflamed and swollen, often due to a viral or bacterial infection. Common symptoms of sinusitis include facial pain and pressure, a congested nose, thick nasal discharge, and a reduced sense of smell.²

Another cause of sinus issues is allergic rhinitis, also known as hay fever. This is an allergic reaction to airborne substances such as pollen, dust mites, and pet dander. Symptoms of allergic rhinitis often include sinus congestion, sneezing, a runny nose, and itchy, watery eyes.

In addition to infections and allergies, sinus pain and congestion can also be caused by structural problems in the nose or sinuses, such as a deviated septum or nasal polyps.

What Role Do the Sinuses Play in Allergies?

The sinuses play a crucial role in allergies, a common condition caused by inflammation of the nasal passages due to an allergic reaction.³

In people who have allergies, when an allergen, such as pollen, dust, or pet dander, enters the airways, the immune system responds by releasing histamine and other chemicals.

These chemicals make blood vessels in the nasal passages and sinuses swell and produce excess mucus, leading to congestion, a runny nose, and other sinus symptoms.

Your body is trying to protect you by expelling the irritant that has entered the body. But sometimes, the immune system overreacts, leading to symptoms that last days or even weeks if the allergen is still present.