How to Know the Difference Between Allergies, Flu and COVID-19

Knowing the difference between allergies, influenza and COVID-19 can feel like navigating a maze when they all target the respiratory system. However, they do have distinctive causes, symptoms and treatments, which are crucial to know for effective treatment. Dr. Peyton Card, an internal medicine physician, covers the differences below.


Allergies occur when the immune system overreacts to a harmless substance, such as pollen, dust mites, pet dander, or certain foods. This reaction triggers the release of histamines and other chemicals, leading to symptoms.

Common allergy symptoms include sneezing, runny or stuffy nose, itching of the eyes, nose, or throat, watery eyes, and sometimes coughing or wheezing. These symptoms are typically not accompanied by fever. They are usually not life-threatening, although they can significantly affect quality of life and productivity.

Treatment for allergies often involves avoiding triggers when possible and using medications such as antihistamines, decongestants, nasal corticosteroids, or allergy shots (immunotherapy) to alleviate symptoms.


Influenza is caused by the influenza virus, which has different strains (such as influenza A and B). It is highly contagious and spreads through respiratory droplets.

Symptoms of the flu can include fever, cough, sore throat, runny or stuffy nose, muscle aches, fatigue, headache, and sometimes vomiting or diarrhea. It can range from mild to severe, and in some cases, it can lead to serious complications in high-risk individuals such as young children, the elderly and those with underlying health conditions.

Treatment for the flu may include antiviral medications if started early, supportive care (rest, fluids, over-the-counter pain relievers), and in severe cases, hospitalization.

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COVID-19 is caused by the SARS-CoV-2 virus, which is a novel coronavirus that emerged in late 2019. Like the flu, it spreads primarily through respiratory droplets.

Symptoms of COVID-19 can vary but commonly include fever or chills, cough, shortness of breath or difficulty breathing, fatigue, muscle or body aches, headache, new loss of taste or smell, sore throat, congestion or runny nose, nausea or vomiting and diarrhea.

COVID-19 can also range from mild to severe. While many people experience mild symptoms, others may develop severe respiratory illness, pneumonia, or acute respiratory distress syndrome (ARDS), especially those with underlying health conditions or older adults.

Treatment for COVID-19 varies depending on the severity of symptoms but may include supportive care, such as rest, fluids, and over-the-counter medications for fever and pain. In severe cases, hospitalized patients may require oxygen therapy, mechanical ventilation, or other supportive measures.

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If you’re unsure about the cause of your symptoms, it’s always best to consult with a healthcare professional for an accurate diagnosis and appropriate treatment plan.