COVID-19, cold, allergies and the flu: What are the differences?

COVID-19, the common cold, seasonal allergies and the flu have many similar signs and symptoms. Find out about some of the important differences between these illnesses.

By Mayo Clinic Staff

If you have signs or symptoms of coronavirus disease 2019 (COVID-19), it's important that you contact your doctor or clinic right away for medical advice. But COVID-19, the common cold, seasonal allergies and the flu (influenza) cause many similar symptoms. So how can you tell if you have COVID-19? Understand the differences in symptoms that these illnesses cause, as well as how these illnesses spread, are treated and can be prevented.

What is COVID-19 (coronavirus), how does it spread, and how is it treated?

COVID-19 is a contagious respiratory disease caused by infection with the virus SARS-CoV-2. It usually spreads between people who are in close contact (within 6 feet, or 2 meters). The virus spreads through respiratory droplets released when someone breathes, coughs, sneezes, talks or sings. These droplets can land in the mouth or nose of someone nearby or be inhaled. The virus can also spread if a person touches a surface or object with the virus on it and then touches his or her mouth, nose or eyes, although this isn't considered to be a main way it spreads.

The most common symptoms of COVID-19 are a fever, cough and tiredness. But there are many other possible signs and symptoms.

Currently, only one antiviral drug, called remdesivir, is approved to treat COVID-19. Some drugs may help reduce the severity of COVID-19. The U.S. Food and Drug Administration has given emergency use authorization for two COVID-19 vaccines.

What’s the difference between COVID-19 and the common cold?

Both COVID-19 and the common cold are caused by viruses. COVID-19 is caused by SARS-CoV-2, while the common cold is most often caused by rhinoviruses. These viruses spread in similar ways and cause many of the same signs and symptoms. However, there are a few differences.

Symptom check: Is it COVID-19 or a cold?

Symptom or sign COVID-19 Cold
Cough Usually (dry) Usually
Muscle aches Usually Sometimes
Tiredness Usually Sometimes
Sneezing Rarely Sometimes
Sore throat Usually Usually
Runny or stuffy nose Usually Usually
Fever Usually Sometimes
Diarrhea Sometimes Never
Nausea or vomiting Sometimes Never
New loss of taste or smell Usually (early — often without a runny or stuffy nose) Sometimes (especially with a stuffy nose)

While COVID-19 symptoms generally appear two to 14 days after exposure to SARS-CoV-2, symptoms of a common cold usually appear one to three days after exposure to a cold-causing virus.

There's no cure for the common cold. Treatment may include pain relievers and over-the-counter cold remedies, such as decongestants. Unlike COVID-19, a cold is usually harmless. Most people recover from a common cold in three to 10 days, although some colds may last as long as two or three weeks.

What’s the difference between COVID-19 and seasonal allergies?

Unlike COVID-19, seasonal allergies aren't caused by a virus. Seasonal allergies are immune system responses triggered by exposure to allergens, such as seasonal tree or grass pollens.

COVID-19 and seasonal allergies cause many of the same signs and symptoms. However, there are some differences.

Symptom check: Is it COVID-19 or seasonal allergies?

Symptom or sign COVID-19 Allergy
Cough Usually (dry) Sometimes
Fever Usually Never
Muscle aches Usually Never
Tiredness Usually Sometimes
Itchy nose, eyes, mouth or inner ear Never Usually
Sneezing Rarely Usually
Sore throat Usually Rarely
Runny or stuffy nose Usually Usually
Pink eye (conjunctivitis) Sometimes Sometimes
Nausea or vomiting Sometimes Never
Diarrhea Sometimes Never
New loss of taste or smell Usually (early — often without a runny or stuffy nose) Sometimes

Also, while COVID-19 can cause shortness of breath or difficulty breathing, seasonal allergies don't usually cause these symptoms unless you have a respiratory condition such as asthma that can be triggered by pollen exposure.

Treatment of seasonal allergies may include over-the-counter or prescription antihistamines, nasal steroid sprays and decongestants, and avoidance of exposure to allergens where possible. Seasonal allergies may last several weeks.

What's the difference between COVID-19 and the flu?

COVID-19 and the flu are both contagious respiratory diseases caused by viruses. COVID-19 is caused by the SARS-CoV-2 virus, while the flu is caused by influenza A and B viruses. These viruses spread in similar ways.

COVID-19 and the flu cause similar symptoms. The diseases can also cause no symptoms or mild or severe symptoms. Because of the similarities, it can be hard to diagnose which condition you have based on symptoms alone. Testing may be done to see if you have COVID-19 or the flu. You can also have both diseases at the same time. However, there are some differences.

Symptom check: Is it COVID-19 or the flu?

Symptom or sign COVID-19 Flu
Cough Usually (dry) Usually
Muscle aches Usually Usually
Tiredness Usually Usually
Sore throat Usually Usually
Runny or stuffy nose Usually Usually
Fever Usually Usually — not always
Nausea or vomiting Sometimes Sometimes (more common in children)
Diarrhea Sometimes Sometimes (more common in children)
Shortness of breath or difficulty breathing Usually Usually
New loss of taste or smell Usually (early — often without a runny or stuffy nose) Rarely

COVID-19 symptoms generally appear two to 14 days after exposure to SARS-CoV-2. Flu symptoms usually appear about one to four days after exposure to an influenza virus.

COVID-19 can cause more-serious illnesses in some people than the flu. Also, COVID-19 can cause different complications than the flu, such as blood clots and multisystem inflammatory syndrome in children.

While there is only one antiviral treatment for COVID-19, there are several antiviral drugs that can be used to treat the flu. Also, you can get an annual flu vaccine to help reduce your risk of the flu. The flu vaccine can also reduce the severity of the flu and the risk of serious complications. The vaccine can be given as a shot or as a nasal spray.

How can you avoid getting COVID-19, a cold and the flu?

You can reduce your risk of infection from the viruses that cause COVID-19, colds and the flu by following several standard precautions. Research suggests that following these measures, such as social distancing and wearing a face mask, might have helped shorten the length of the flu season and lessened the number of people affected in the 2019-2020 flu season.

Standard precautions to reduce your risk of COVID-19, colds and the flu include:

  • Avoiding close contact (within 6 feet, or 2 meters) with anyone outside your household, especially if you have a higher risk of serious illness
  • Wearing a cloth face mask when you're in public spaces, such as the grocery store, where it's difficult to avoid close contact with others
  • Washing your hands often with soap and water for at least 20 seconds, or using an alcohol-based hand sanitizer that contains at least 60% alcohol
  • Avoiding crowded indoor spaces
  • Covering your mouth and nose with your elbow or a tissue when you cough or sneeze
  • Avoiding touching your eyes, nose and mouth
  • Cleaning and disinfecting high-touch surfaces, such as doorknobs, light switches, electronics and counters, daily

Also, get an annual flu vaccine and, when possible, get a COVID-19 vaccine.

How can you prevent allergies?

The best way to prevent seasonal allergies is to avoid your known triggers. If you're allergic to pollen, stay inside with windows and doors closed when pollen is high.

Wearing a cloth face mask to slow the spread of COVID-19 also might provide some protection against seasonal allergies. Masks can prevent you from inhaling some larger pollen particles. However, smaller pollen particles will still be able to get through a mask. It's also important to wash your mask after each use since a mask might carry pollen particles.

If you think you might have signs or symptoms of COVID-19, talk to your doctor. Remember, taking preventive measures can help you stay healthy and reduce your risk of becoming ill with COVID-19, the flu or the common cold.

Dec. 22, 2020 See more In-depth

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