How to tell if symptoms are due to allergies, the common cold, the flu, or COVID-19

Spring and summer have a lot to offer—warmer weather, pretty flowers, and relaxing vacations. For some people, however, they also bring on the dreaded seasonal allergies and the sneezing and sniffling that go with them.

According to Deborah Erlich, M07, vice chair for education and associate professor of family medicine at Tufts University School of Medicine, this allergy season is longer as well as more intense than in previous years.

“A recent report posited that climate change is a factor,” she says. “The warm spring weather has been starting a few weeks sooner than in past years, and fewer days of frost give plants and flowers the chance to develop more pollen.”

Since allergies share common symptoms with other upper respiratory conditions, including colds, flu, and COVID-19, it’s not always easy to identify which of these is making you feel miserable.

“Seasonal allergies are not life-threatening, but they are bothersome and can last weeks or months,” says Erlich. “On the other hand, viral respiratory infections are short-lived, but usually more symptomatic. Worse, they carry a risk of a secondary infection like pneumonia.”

Tufts Now asked Erlich how to know if you have allergies or something else.

Tufts Now: Why might it be hard to tell if you have allergies or a viral infection?

Deborah Erlich: Seasonal allergies reflect the release of histamine in response to an allergen. That histamine release causes similar symptoms—such as runny nose, sneezing and congestion—as the common cold, influenza, COVID-19, or other viral infections. Since there is overlap in symptoms, it can sometimes be hard to distinguish between seasonal allergies and other conditions.

What are some of the clues that you might have allergies versus a cold or something else?

Early symptoms can be similar, though allergies can cause itchy eyes, which is less common in viral infections. Also, fevers tend to signify infections. Allergies tend not to produce fevers. Allergies are likely to have more sudden onset after the trigger. For example, someone allergic to pollen might notice symptoms after just a few minutes outdoors. Someone allergic to cats will start to feel symptoms after exposure to cats. Seasonal allergies will last throughout the season and usually return year after year, while colds and flu happen intermittently after exposure to a virus.

When in doubt, take a COVID-19 test. It’s easy to do. Many people have falsely attributed their symptoms to allergies when they really had COVID and ended up transmitting the virus to others.

What is your advice on how to treat seasonal allergies?

Start by avoiding the triggers. Mitigate pollen allergies by keeping windows closed, using air purifiers at home, running the air conditioner, and staying indoors when possible. Consider taking shoes off at the entrance to your home so that you do not track grass or pollen through the house.

There are also several very effective over-the-counter medications. Oral antihistamines are best. Some cause more drowsiness than others. Avoid using oral decongestants for a long period of time. Decongestants work by constricting blood vessels, providing temporary relief of a congested nose, but can be dangerous for people with high blood pressure, heart disease, or glaucoma.

Patients with those conditions should avoid decongestants altogether. In addition, anyone taking medications for a chronic condition should check with their doctor before using any medication containing a decongestant. For otherwise healthy people, taking oral decongestants for more than three to five days can cause rebound congestion.

Over-the-counter nasal steroids are safe and work well for runny nose and congestion. Some patients also like to use nasal saline to keep the nasal passages lubricated. Itchy or watery eyes tend to respond best to antihistamine eye drops, also available over the counter.

Patients who experience wheezing with their allergies may suffer from allergy-induced asthma or year-round asthma. Either way, a prescription inhaler may help open the airways, even if it is only used during allergy season. A second line treatment I often prescribe for patients with allergies, especially with concomitant asthma, is montelukast, a leukotriene inhibitor. This is usually along with another prescription inhaler from a different family.

When would someone want to consider immunotherapy for seasonal allergies?

Immunotherapy is reasonable when none of the other medications is helpful and the patient is still suffering. Tiny amounts of allergen are injected to trigger a mini immune response in order to desensitize the body. Over time, the dose is increased so that eventually the body can handle a full dose of allergen (e.g., pollen) without reacting.

What kinds of symptoms warrant a call to your doctor?

Symptoms that continue regardless of treatment warrant a call. It is also reasonable to call if there are symptoms that do not fit the typical picture of allergies, such as fever. Always call if there is difficulty breathing, wheezing, or shortness of breath.

Finally, it’s quite unpleasant to suffer from allergies at the same time as a viral respiratory infection. So those who are prone to allergies should be vigilant about handwashing, avoiding touching their face and eyes, keeping distant from others who are visibly ill with respiratory infections, and getting an influenza vaccine for protection every year.