Flu, COVID-19, cold, allergies—what’s the difference?

Reviewed 3/21/2024

Because many illness symptoms are similar, it may be difficult for you to decide whether your child picked up a virus or is experiencing allergies as the seasons change. As we continue to navigate this pandemic, it’s more important than ever for your child to stay at home if they are showing any symptoms of an illness.

When a child starts feeling sick, it’s often a challenge for parents to figure out what illness their kid has—and how serious it is. Is it a cold, the flu or COVID-19? Or your child may be suffering from allergies, or a different virus.

We know it’s hard to determine which illness your child is suffering from because cold, flu and COVID-19 symptoms are common. If your child is exhibiting any symptoms at all, you should keep them at home.

Because colds, RSV, the flu and COVID-19 are caused by viruses, these illnesses do not get better with the antibiotics that would be used to treat a bacterial infection.

“It’s important for parents to remember that we often treat these viruses the same way—with at-home care that includes fluids, rest and over-the-counter pain or fever reducers, as needed,” says Andi Shane, MD, MPH, MSc, System Medical Director, Infectious Diseases at Children’s Healthcare of Atlanta. “As a parent, it’s important to trust your instincts: call your child’s doctor if you have concerns and know the symptoms that warrant medical care,” adds Dr. Shane.

How can I keep the rest of my family well?

If you have sick kids, or other family members in your home with any symptoms, try to distance them from people without symptoms. Teach children how to wash their hands and how to use a hand sanitizer.

Girl with the flu blowing nose

Allergies occur when the body produces an abnormal immune response to something in the environment or something that is consumed. Allergies can be seasonal or can occur when children encounter an allergen—such as something they ate or environmental factors like pollen or dust. Allergies are more likely to occur at certain times of the year, usually fall and spring, and are less likely to affect babies and toddlers.

Symptoms of allergies may include:

  • Runny nose
  • Sniffling
  • Sneezing
  • Itchy, watery eyes

Colds are caused by an infection of the upper respiratory tract (nose, throat, sinuses and windpipe). Cold viruses are contagious, so they spread easily. Symptoms of a cold usually peak within two to three days and may include:

  • Cough
  • Sore throat
  • Runny or stuffy nose
  • Watery eyes
  • Sneezing

Respiratory syncytial virus (RSV) infection is a viral illness that can cause people to have trouble breathing. It mostly affects the very young and is extremely common—almost all children will have an RSV infection by their second birthday. A child’s first RSV infection is usually the most severe, and children who are born prematurely or have breathing or heart problems are more likely to have complications from an RSV infection. Symptoms of an RSV infection may include:

  • Runny nose
  • Decreased appetite
  • Coughing
  • Sneezing
  • Fever
  • Wheezing

These symptoms usually appear in stages and not all at once. Children infected with RSV usually show symptoms within four to six days after getting infected. In very young infants with RSV, the only symptoms may be irritability, poor feeding, decreased activity and breathing difficulties.

COVID-19 is caused by SARS-CoV-2, a respiratory virus that causes a range of symptoms. Not everyone infected with the virus will have all these symptoms. Some people with COVID-19 become severely ill, others have mild symptoms and still others show no symptoms at all—but may transmit the virus without getting sick themselves. Symptoms tend to appear from two to up to 14 days after exposure to the virus, although most people develop symptoms within the first week after exposure.

Symptoms of COVID-19 infection may include:

  • Cough
  • Brief episodes of fever
  • Shortness of breath
  • Abdominal pain
  • New loss of taste or smell
  • Congestion
  • Fatigue
  • Sore throat
  • Nausea or vomiting
  • Diarrhea
  • Muscle or body aches
  • Headache

At-home COVID tests are easy and convenient, but are they accurate?

Children’s researchers are leading studies to help ensure that rapid COVID-19 tests are as accurate as possible today and in the future, no matter what variants come our way.

Get Informed

The seasonal flu (influenza) can cause mild to severe illness, and it can even cause serious complications that can lead to death. The flu usually comes on very suddenly; your child may feel perfectly fine one day and be very sick the next, unlike COVID-19, which tends have gradual symptom onset.

Symptoms of the flu may include:

  • Fever
  • Chills
  • Headache
  • Runny nose
  • Nausea
  • Fatigue
  • Loss of appetite
  • Sore throat

Getting the flu shot for you and your family is the best way to protect your family from having severe infections or contracting the infection at all.

Since some flu symptoms are like symptoms of COVID-19, preventing a flu infection by getting your annual flu shot could reduce confusion or concerns about possible COVID-19 infection in your family. Remember, it’s never too late to get a flu shot.

“It is very, very important for parents to make sure that they and their children receive their flu vaccines each year,” Dr. Shane says. “It’s something parents can actively do to protect children and themselves. In addition, everyone who is age eligible should receive COVID-19 vaccinations. Two shots equal protection against two unpredictable diseases.”

COVID-19 has many similarities to the flu, since they’re both contagious respiratory viruses. Here are some key differences between the two.

What are the biggest differences between COVID-19 and the flu?

Most children who have the flu experience rapid onset of symptoms and start to feel sick with a fever, cough and runny nose for several days.

In contrast, children with COVID-19 may not have any symptoms or may have a fever for a short period of time accompanied by congestion, a cough, and loss of taste and smell.

What should I do if my child has symptoms?

Because any symptom could mean that your child could be infectious with a virus, you should keep your kids at home if they are experiencing any of these symptoms.

“If your child has any symptoms, keep him at home,” says Dr. Shane. “Have him remain at home for 24 hours to see if symptoms progress.”

Seek medical care right away if your child is showing any of these symptoms:

  • Trouble breathing
  • Pain or pressure in the chest that does not go away
  • New confusion
  • Inability to wake or stay awake
  • Bluish lips or face
  • Severe abdominal pain
  • Refusing to eat and drink

Andi L. Shane, MD, MPH, MSc, is Medical Director of Infectious Diseases at Children’s Healthcare of Atlanta. Dr. Shane completed an Epidemic Intelligence Service (EIS) fellowship at the Centers for Disease Control and Prevention (CDC) and a pediatric infectious disease fellowship at the University of California San Francisco. Dr. Shane has broad experience and interests in the field of pediatric infectious diseases and is committed to the care of children with infections with special pathogens in protected care environments working with children’s hospital preparedness teams.

This content is general information and is not specific medical advice. Always consult with a doctor or healthcare provider if you have any questions or concerns about the health of a child. In case of an urgent concern or emergency, call 911 or go to the nearest emergency department right away. Some physicians and affiliated healthcare professionals on the Children’s Healthcare of Atlanta team are independent providers and are not our employees.