MNT Investigates: How do seasonal allergies and asthma affect nasal polyps?

What is the link between nasal polyps, seasonal allergies, and asthma?

“Nasal polyps are growths inside of the nose that often grow in response to chronic inflammation within the nasal passages,” explained Alan D. Workman, MD, MTR, a sinus surgeon at Massachusetts Eye and Ear and assistant professor at Harvard Medical School.

Inflammation occurs due to an overactive immune system, which can lead to swelling and irritation of the nasal mucosa (the lining inside the nose). Over time, this prolonged inflammation can permanently damage the healthy tissues of the nasal passage. This may lead to an overgrowth of the nasal tissue, known as a polyp.

Various respiratory conditions can cause inflammation in the nasal passages and have a link with CRSwNP.

Asthma and nasal polyps

Asthma is one of the most well-studied associations with CRSwNP. Research suggests that anywhere from 20% to 60% of people with CRSwNP also have asthma.

“Asthma and nasal polyps are very often seen together, as asthma is also a disease of over-reactive airway inflammation,” explained Workman. “The cycles of inflammation seen in asthma and nasal polyps often co-occur and can worsen each other.”

There is also aspirin-exacerbated respiratory disease (AERD), which is a condition of asthma and nasal polyps that also includes a sensitivity or allergy to aspirin. In people with AERD, using aspirin can incite an inflammatory response that worsens asthma symptoms. “These people often have the most severe nasal polyps and asthma and require a comprehensive treatment strategy,” said Workman.

Seasonal allergies and nasal polyps

A report published in 2024 by the Asthma and Allergy Foundation of America notes that up to 80% of people with CRSwNP may also have allergic rhinitis.

“Allergies trigger nasal inflammation, and chronic sinusitis with nasal polyps is also a disorder of unchecked nasal inflammation,” said Workman.

However, more research is needed to fully understand this link.

Can seasonal allergies or asthma cause nasal polyps?

Even though there is a link between nasal polyps, allergies, and asthma, there is still some debate about how they develop, added Mark Moss, MD, an allergy, asthma, and immunology specialist at the University of Wisconsin.

“Some experts believe that allergies lead to nasal polyps, some believe infection leads to nasal polyps, and some believe that they both contribute,” he said.

He also emphasized that these relationships are variable and that not everyone with asthma or allergies will develop nasal polyps. Even among people with asthma — a condition strongly associated with nasal polyps — only about 7% develop CRSwNP.

Workman noted that the same is true for people with allergies. “Many people get seasonal allergies that make them feel congested at times, but only a smaller percentage have nasal polyps,” he said.

In addition to allergies or asthma, other risk factors that may cause nasal inflammation and predispose people to the development of nasal polyps include:

• repeated sinus infections
• nasal trauma or surgery
• long-term exposure to allergens or irritants, such as pet dander or tobacco smoke
• family history of nasal polyps

Can seasonal allergies or asthma make nasal polyps worse?

Unmanaged allergy or asthma symptoms can lead to more inflammation and subsequent swelling of nasal polyps. This can further contribute to blockage of the nasal passages, worsening symptoms and making it harder to breathe.

The reverse is also true. People with nasal polyps may experience worsened seasonal allergies or asthma symptoms. In fact, people who have asthma and CRSwNP may be at an increased risk of developing a more severe case of asthma than those without CRSwNP.

“[Nasal polyps] enlarge and block the drainage of the sinuses, leading to nasal congestion, loss of sense of smell, and infection of the sinuses,” said Moss. This can lead to difficulty breathing as well as a variety of nasal symptoms, such as:

• a stuffy or running nose
• facial and dental pressure or pain
• postnasal drip

How are nasal polyps treated in people with asthma or allergies?

Management of nasal polyps in people with asthma, allergies, or other inflammatory respiratory diseases often requires a comprehensive approach to care.

“When people have nasal polyps as well as moderate to severe asthma,” said Workman, “ear, nose, and throat (ENT) doctors will often team up with allergists and/or pulmonologists to collaborate and address each component of the inflammation.

“For asthma and nasal polyps, oral corticosteroids are very effective at improving symptoms but cannot be given over long periods of time as they can have effects on all aspects of the body,” said Workman. “For this reason, first-line steroid therapies for asthma and nasal polyps are often delivered locally, such as with an inhaler in asthma or in a spray or salt-water rinse for sinusitis with polyps.”

“These therapies still have a role, but today, there are better mediations that are much safer,” added Moss. “The addition of biologic treatments has completely changed the care that can be offered to people with asthma and nasal polyps.”

Biologics are a type of medication that target the specific molecules that contribute to inflammation in asthma and nasal polyps. There are three biologics approved for the treatment of CRSwNP, all of which doctors can also use to help treat asthma:

• dupilumab (Dupixent)
• mepolizumab (Nucala)
• omalizumab (Xolair)

Studies with dupilumab suggest that this biologic is effective for treating CRSwNP in people with comorbid conditions such as allergies and asthma. In the asthma trial, 71% of people with CRSwNP and oral corticosteroids-dependent asthma were able to stop steroid treatment within 96 weeks of starting treatment with dupilumab.

These biologic therapies involve an injection (shot) every few weeks.

Takeaway

Nasal polyps are common among people with asthma or seasonal allergies. They develop as a result of ongoing inflammation within the nasal passages. Left untreated, nasal polyps can contribute to worsening respiratory symptoms.

Management of nasal polyps in people with asthma, allergies, or other inflammatory respiratory diseases may involve working with multiple specialists to treat any underlying inflammation in the body.