For the third year in a row, seasonal allergies have coexisted with COVID-19. And according to clinicians, it has been increasingly difficult to tell the two apart.

As spring progresses and pollen counts rise, more people are starting to wonder if their stuffy nose is a sign of COVID or allergies. “It’s almost impossible to differentiate them,” says infectious disease doctor Aaron Glatt, chair of medicine at Mount Sinai South Nassau and a spokesperson for the Infectious Diseases Society of America.

“Each COVID-19 strain has different symptoms. The Omicron variant, more than the others, seems to have more of the upper respiratory tract symptoms like nasal congestion, runny nose and sore throat,” says otolaryngologist Ahmad Sedaghat, director of the Division of Rhinology, Allergy and Anterior Skull Base Surgery at the University of Cincinnati College of Medicine. All of these effects coincide with allergy symptoms, as well as sneezing, coughing, headaches and tiredness, according to the U.S. Centers for Disease Control and Prevention.

Getting a COVID test is the most efficient way to know for sure, but it can take days to test positive after developing symptoms. Still, there are a few peculiarities that may help distinguish between COVID and allergies. The predominant form of COVID in the U.S. is Omicron’s subvariant BA.2. As of April 30, it was responsible for almost 62 percent of infections in the country. The fact that Omicron tends to cause less severe disease than previous variants contributes to further confusion about whether or not one’s symptoms are allergies.

Telltale Differences

“Probably the one symptom that would pretty much rule out allergies would be fever,” says allergist Janna Tuck, a spokesperson for the American College of Allergy, Asthma and Immunology. Although allergic rhinitis is commonly known as “hay fever,” an elevated temperature is not a symptom associated with allergies. “If somebody is having fever, you can pretty much guarantee that they have a viral illness,” Tuck notes.

Another symptom that points toward COVID is severe smell loss, or anosmia. “When smell loss occurs in the setting of COVID-19, in the vast majority of cases, it is sudden and profound,” Sedaghat says. He notes that allergies may also cause a diminished sense of smell because nasal congestion can prevent odorant molecules from reaching the top of the nose, where the olfactory receptors and nerves are. In that case, it is often a partial smell loss, as opposed to the severe anosmia observed in many COVID patients.

Sedaghat studies a condition called chronic rhinosinusitis, which is also associated with an altered sense of smell, and his team was one of the first to describe the severity of olfactory problems in COVID patients. But he notes that this symptom is fairly rare among Omicron infections. In a recent study published in the International Forum of Allergy & Rhinology, about 25 percent of COVID patients reported an altered sense of smell earlier this year, when Omicron was the dominant variant, compared with almost 63 percent of patients who did so earlier in the pandemic.

Watery eyes and puffy eyelids—which are not typically seen in COVID—also point to allergies, according to Glatt. (COVID can cause eye issues such as conjunctivitis, however.) The duration of symptoms may also be suggestive. Whereas mild COVID symptoms usually clear up within a couple of weeks, allergies can drag on longer, Sedaghat notes.

Know Your Own Body

Clinicians say that paying attention to your individual medical history may help distinguish allergies from COVID. “Most of the time, for adults who tend to have seasonal allergies, they know that every [spring] they’re going to have the same symptoms,” Tuck says. “If they’ve been paying attention, they will know if the symptoms they’re experiencing are more likely to be their seasonal allergies.”

The context is also important. “If an individual starts having symptoms right after they mowed the lawn or did yard work or cleaned out a dusty attic or even sat out in their backyard on a freshly warm day, that could be a stronger indication of allergies,” Sedaghat says. If, on the other hand, the symptoms start after an indoor gathering where you were potentially exposed to someone who was sick, that may point toward COVID.

What if It’s Still Not Clear?

If the symptoms are too nonspecific to make an informed guess, clinicians strongly advise taking a COVID test. “Tests are so easily available now. If a person is concerned, they should do a COVID test. That’s the easy answer,” Glatt says. If the result of a rapid test is negative and the symptoms persist, you might want to consider testing again in a day or two. It might be too early in the disease for the virus to be detectable.

Regardless of whether you have allergylike symptoms, if you know you had close contact with someone with COVID, you should get tested at least five days after exposure, according to the CDC. Even if you have seasonal allergies, that does not mean you cannot also get COVID. This recommendation is especially important for adults working in person and children attending school, Tuck adds.

The process of deciding whether you should quarantine is more complex. It should be made on a case-by-case basis, depending on many factors, including your vaccination status, whether you had COVID in the past three months and whether you were recently exposed to a sick person. The CDC has a quarantine and isolation calculator that can help you make that decision.

The Interplay between Allergies and COVID

Early in the pandemic, allergists were concerned, based on their experience with influenza, that patients with allergic asthma were at a higher risk of developing severe COVID. But that turned out not to be the case. “These patients did not do poorly with COVID, which we were all very relieved about,” Tuck says. “They actually did better than we expected.”

In fact, a study published in the journal Thorax found that people with allergic asthma may be at a lower risk of COVID infection, compared with those without the condition. Sedaghat notes that recent evidence suggests people who produce allergic inflammation may have a lower risk of producing the nonallergic type of inflammation associated with severe COVID. “We’ve seen, in some studies, that patients who tend to have allergic inflammation have lower levels of the receptor for the virus that causes COVID-19.”

Fortunately, wearing a mask helps protect against both COVID and seasonal allergies. Pollen particles are relatively large, and masks effectively keep them away from the nose and mouth. Observing this incidental benefit was one of the pandemic’s silver linings, Sedaghat says. “As a clinician, all I see and treat are patients with allergies and sinus problems. These patients had a dramatic benefit from wearing masks. It was unbelievable how much better they were doing,” he says.

Now that masks are no longer mandatory in many settings, Sedaghat reminds his patients about their benefits—including the freedom to enjoy the outdoors without suffering from streaming eyes and sinuses.