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

Date Updated: 11/03/2023

If you have symptoms of coronavirus disease 2019 (COVID-19), it's important that you contact your health care professional right away for medical advice. But COVID-19, the common cold, seasonal allergies and the flu, also called influenza, cause many similar symptoms. So how can you tell if you have COVID-19?

Understand the differences in symptoms that these illnesses cause. And find out how these illnesses spread, are treated and can be prevented.

What is COVID-19, 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. 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 also can spread if you touch a surface or object with the virus on it and then touch your mouth, nose or eyes. But this risk is low.

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

Many people with COVID-19 may have mild illness and can be treated with supportive care. Currently, a few medicines have been approved to treat COVID-19. No cure is available for COVID-19. Antibiotics aren't effective against viral infections such as COVID-19. Researchers are testing a variety of possible treatments.

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. All of these viruses spread in similar ways and cause many of the same symptoms. However, there are a few differences.

Symptom check: Is it COVID-19 or a cold?
Symptom	COVID-19	Cold
Headache	Usually	Rare
Cough	Usually (dry)	Usually
Muscle aches	Usually	Sometimes
Tiredness	Usually	Sometimes
Sneezing	Rarely	Usually
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)

COVID-19 symptoms usually start 2 to 14 days after exposure to SARS-CoV-2. But symptoms of a common cold usually appear 1 to 3 days after exposure to a cold-causing virus.

There's no cure for the common cold. Treatment may include pain relievers and cold remedies available without a prescription, such as decongestants. Unlike COVID-19, a cold is usually harmless. Most people recover from a common cold in 3 to 10 days. But 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 symptoms. However, there are some differences.

Symptom check: Is it COVID-19 or seasonal allergies?
Symptom	COVID-19	Allergy
Headache	Usually	Rare
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

COVID-19 can cause shortness of breath or difficulty breathing. But 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 nonprescription 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. The flu is caused by influenza A and B viruses. All of these viruses spread in similar ways.

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

Symptom check: Is it COVID-19 or the flu?
Symptom	COVID-19	Flu
Headache	Usually	Usually
Cough	Usually (dry)	Usually
Muscle aches	Usually	Usually
Tiredness	Usually	Usually
Sore throat	Usually	Usually
Runny or stuffy nose	Usually	Usually
Fever	Usually	Usually
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 2 to 14 days after exposure to SARS-CoV-2. Flu symptoms usually appear about 1 to 4 days after exposure to an influenza virus.

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

There are a few antiviral treatments 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 also can 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.

For COVID-19, you can get a 2023-2024 COVID-19 vaccine to reduce the risk of getting seriously ill with COVID-19.

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

The COVID-19 vaccine can lower the risk of death or serious illness caused by COVID-19. It lowers your risk and lowers the risk that you may spread it to people around you. The CDC recommends a COVID-19 vaccine for everyone age 6 months and older.

The COVID-19 vaccines available in the United States are:

2023-2024 Pfizer-BioNTech COVID-19 vaccine, available for people age 6 months and older.
2023-2024 Moderna COVID-19 vaccine, available for people age 6 months and older.
2023-2024 Novavax COVID-19 vaccine, available for people age 12 years and older.

Get a flu vaccine too. Getting an annual flu vaccine will lower your risk of getting the flu. It can be given as a shot or as a nasal spray. The flu vaccine also lowers the chance you'll have a serious case of flu. It also lowers the risk of serious complications.

You can lower your risk of infection from the viruses that cause the common cold, flu and COVID-19 by following some standard safety measures.

Research suggests that following these measures, such as physical 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.

Follow these standard precautions:

Get vaccinated against flu and COVID-19.
Avoid close contact with anyone who is sick or has symptoms.
Keep distance between yourself and others when you're in indoor public spaces. This is especially important if you have a higher risk of serious illness. Keep in mind that some people may have COVID-19 and spread the COVID-19 virus to others even if they don't have symptoms or don't know they have COVID-19.
Wear a face mask in indoor public spaces if you're in an area with a high number of people with COVID-19 in the hospital. The CDC recommends wearing the most protective mask possible that you'll wear regularly, fits well and is comfortable.
Wash your hands often with soap and water for at least 20 seconds, or use an alcohol-based hand sanitizer that contains at least 60% alcohol.
Avoid crowded indoor spaces and indoor places that have poor air flow, also called ventilation.
Improve the air flow indoors. Open windows. Turn on fans to direct air out of windows. If you can't open windows, consider using air filters. And turn on exhaust fans in your bathroom and kitchen. You also might consider a portable air cleaner.
Cover your mouth and nose with the inside of your elbow or a tissue when you cough or sneeze. Throw away the used tissue. Wash your hands right away.
Avoid touching your eyes, nose and mouth.
Avoid sharing dishes, glasses, towels, bedding and other household items if you're sick.
Regularly clean and disinfect high-touch surfaces, such as doorknobs, light switches, electronics and counters.
Stay home from work, school and public areas and stay in isolation at home if you're sick, unless you're going to get medical care. Avoid public transportation, taxis and ride-hailing services if you're sick.

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 there's a lot of pollen in the air.

Wearing a face mask also might provide some protection against seasonal allergies. Masks can prevent you from inhaling some larger pollen particles. However, smaller pollen particles can 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 symptoms of COVID-19, talk to your health care professional. Remember, taking preventive measures can help you stay healthy.