You wake up with a stuffy nose and a mild headache. Before the pandemic, this was no big deal. You just had to figure out if you had a cold or the flu. In spring or fall, maybe you’d throw seasonal allergies into the mix. But COVID-19 has changed all of that. Now it can feel like you need a medical degree to decide whether you should get tested for this new illness.

If you’ve been fully vaccinated and boosted against COVID-19, the symptoms of a breakthrough infection are similar to those of a cold or the flu. And with the rise of the highly contagious Omicron variant during the latest surge, breakthrough infections have become more common in fully vaccinated people.

(It’s important to note that vaccines are highly effective at preventing serious illness, hospitalization and death. COVID-19 can be severe or fatal, however, in people who are unvaccinated, especially those in high-risk groups.)

All this complicates an already confusing situation. How do you know whether you have a cold, the flu, COVID-19 or allergies? Experts walk you through the differences.

From at-home tests to at-home care, Optum’s COVID-19 resource center is here for you.

The concerns with COVID-19

It was bad enough when colds, the flu and allergies were circulating together. Now that COVID-19 has joined the mix, the potential for worse outcomes is higher, especially if you’re not fully vaccinated or you’re unvaccinated. And doctors are certainly worried.

“One of the biggest concerns I have is complacency,” says Phillip Kadaj, MD. He’s an internal medicine physician and medical expert with JustAnswer.com. “People are still getting hospitalized from COVID, and it is a serious disease. This is especially true for people who are at high risk for complications from COVID, such as the elderly or those with multiple medical problems.”

And among unvaccinated people, the risk of death is 97 times higher than those who have gotten vaccinated and boosted, according to a White House press briefing in early February.

Health experts also point out that fewer people are getting the flu than they did before the pandemic. There may be reasons for that.

“Most doctors I’ve talked with agree that masking up, social distancing and taking other precautions have prevented the transmission of these respiratory diseases,” says Neil Schachter, MD. He’s the medical director of pulmonary rehabilitation at Mount Sinai Hospital in New York City and the author of The Good Doctor’s Guide to Colds and Flu. “In a sense, it’s COVID until proven otherwise,” he says.

Sorting out COVID-19, cold and allergy symptoms

There is a fair amount of crossover in the symptoms of a cold, the flu, COVID-19 and allergies. Here are the main symptoms of each, according to Dr. Schacter and Dr. Kadaj:

Cold

• Runny nose
• Sore throat
• Cough
• Fatigue
• Congestion
• Mild aches
• Malaise
• Low-grade fever (below 100.4° F)

Flu

• Moderate to high fever
• Chills
• Sweats
• Headache
• Dry cough
• Shortness of breath
• Congestion
• Runny nose
• Vomiting
• Diarrhea

COVID-19

• Fever
• Cough
• Headache
• Congestion
• Malaise
• Loss of taste or smell
• Shortness of breath
• Chest pain
• Diarrhea

Allergies

• Runny nose
• Itchy eyes
• Congestion
• Post-nasal drip
• Sneezing

Luckily, there are some differences that might clue you in as to what you have. “Influenza and COVID tend to produce more severe symptoms,” Dr. Kadaj says. That includes a higher fever, body aches, shortness of breath, a bad headache and exhaustion. “Cold and allergy symptoms tend to be milder.”

Gastrointestinal symptoms, such as nausea, vomiting and diarrhea, also might point to COVID-19. “These would be very unusual in colds and allergies,” Dr. Schachter says. It’s not impossible to have stomach issues with the flu, but it happens more often with COVID-19.

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And while having a cold, allergies or the flu can affect your sense of taste and smell, it’s usually due to nasal congestion. You should suspect COVID-19 if you’re not congested and you suddenly can’t smell things. That is often one of COVID-19’s earliest symptoms. It happens when the virus infects nerve cells in the nasal passages.

With seasonal allergies, you won’t have a fever or severe symptoms. Allergies strike when your immune system overreacts to something in the environment, such as pollen or grass. If you’re sneezing and have a runny nose, allergies might be the culprit.

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Home treatment options for every illness

Figuring out what you have is crucial for helping prevent the spread of transmissible diseases. It can also help you choose the right treatments. Here’s what to do:

Keep your distance. Stay away from others if you’re not feeling well — regardless of whether it’s COVID-19 or not, Dr. Kadaj says.

If you have a sore throat, cough, body aches and especially fever, you should assume it’s COVID-19 until you test negative. A PCR test taken at a doctor’s office or testing clinic is the most accurate option, Dr. Schachter says. If you test positive with an at-home rapid test, you should follow up with your doctor to confirm your diagnosis. (Stock up now on COVID-19 home tests.)

If it is COVID-19, follow the current quarantine protocols recommended by the Centers for Disease Control and Prevention.

Treat it at home. The same treatments can often apply to colds, flu and COVID, Dr. Schachter says. Take acetaminophen (Tylenol®) or ibuprofen (Advil®) for headaches and mild fever, antihistamines for a stuffy nose, and lozenges and throat gargles for a sore throat. Drink lots of fluids and get plenty of rest. 

Be alert. Pay close attention to your symptoms, especially if you're COVID-19 positive. “Keep in touch with your physician if you’re older, have high blood pressure or diabetes, or are obese,” Dr. Schachter says. These could put you at risk of more severe issues, and you should alert your doctor if you’re feeling sick.

Deciphering which illness you have does take some detective work. But getting it right could help you recover more easily — and keep others safe at the same time.

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