Health Info > Coughs Published on : April 27, 2025

Cough: COVID-19, flu, cold, RSV, or allergies – how to tell?

Name: Hola Health
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Written by the editorial staff writer at Hola. Medically Reviewed by Dr. Ammar AL-ANI, MBChB, CCBST, AMC.

Cough: COVID-19, flu, cold, RSV, or allergies – how to tell?

Summary: Coughing can stem from COVID-19, the flu, a cold, RSV, or allergies. While these conditions share symptoms, key differences like the nature of the cough, onset, and additional signs can help distinguish them. Seeking advice from a healthcare professional is vital for accurate diagnosis and treatment, especially if symptoms are intense and ongoing.

Coughing is a common symptom seen in people with different respiratory conditions. However, it can be difficult to distinguish whether the cough is caused by COVID-19, the flu, a cold, respiratory syncytial virus (RSV), or allergies. These ailments share some similar symptoms, but there are subtle differences that may help identify the cause of the cough. In Australia, nearly 5,000 cases were recorded in the National Notifiable Disease Surveillance System in January. Let’s examine these conditions, highlighting how to differentiate them by the nature of the cough, additional symptoms, and the progression of the illness.

How does this cough sound?

Coughing is a common symptom of various respiratory illnesses, including COVID-19, the flu, the common cold, RSV, and allergies. Although all these conditions can cause a cough, the type and the sound of the cough can help distinguish them. Here’s how the cough sounds for each condition:

COVID-19:

Type: Dry, irritating, and persistent. About two-thirds of coughs related to COVID-19 are dry.
Sound: Unproductive and harsh, often mucus-free.

Flu:

Type: Productive (wet) cough
Sound: Wet, congested, and chesty.

Common cold:

Type: Mild, often dry or slightly wet.
Sound: Cough is light, often intermittent.

RSV:

Type: Wet and phlegm-producing.
Sound: Wheezing or rattling, especially in young children.

Allergies:

Type: Dry, tickling cough
Sound: Occurs intermittently, triggered by allergens.

Coughs vary depending on the condition. COVID-19 usually causes a dry, persistent cough, while the flu brings about a wet, mucus-filled, chesty cough. The common cold produces a mild, occasional cough, either slightly moist or dry. RSV causes a wet, mucus-producing, often wheezing or gurgling cough, especially in children. Allergies provoke a dry, tickling cough in spurts, usually triggered by allergens.

Duration

Here’s the duration of each type of cough:

COVID-19: The cough may persist for weeks or even longer if complications arise (like post-viral cough
Flu: Usually lasts 1-2 weeks, with the cough improving as other symptoms resolve.
Common cold: Generally, lasts 7-10 days, with the cough easing gradually.
RSV: It may last 1-2 weeks, but in severe cases, the cough and symptoms may endure longer, especially in infants.
Allergies: Last as long as allergen exposure continues, often seasonal.

Other conditions like fever, nausea, diarrhoea

Alongside a cough, symptoms such as fever, nausea, and diarrhoea can assist in differentiating between COVID-19, flu, cold, RSV, and allergies.

Fever: This is often found in cases of COVID-19 and flu but is uncommon with colds, RSV, and allergies. A notable fever (over 40°C) is typically associated with the flu and COVID-19.
Nausea and vomiting: These are more frequent with the flu and COVID-19, particularly in children. Allergies and colds generally do not induce nausea.
Diarrhoea: This can happen with COVID-19 and flu but is rare with colds, RSV, and allergies. COVID-19 may lead to digestive problems even in the absence of respiratory symptoms.

If symptoms are severe or ongoing, it's crucial to consult a GP to identify the cause and receive appropriate care.

Additional symptoms

Coughing is a frequent symptom of several illnesses, including COVID-19, flu, colds, RSV, and allergies. However, these ailments usually come with other symptoms that help differentiate one from another. Recognising additional signs like fever, nausea, body aches, and breathing difficulties can offer insights into the underlying cause and direct suitable treatment.

COVID-19

Fever or chills
Difficulty breathing
Loss of taste or smell
Tiredness
Muscle aches
Headache
Sore throat

Also read: Long COVID: Symptoms, risk factors, and treatment options

Flu

Abrupt high fever
Severe body aches
Chills
Tiredness
Headache
Sore throat
Runny or congested nose

Also read: Flu Stages: A Day-by-Day Guide and Recovery

Common cold

Sneezing
Runny or congested nose
Mild sore throat
Mild cough
Low-grade fever (rare)
Mild tiredness

Also read: How to Get Rid of a Cold: Medically Approved Home Remedies

RSV (Respiratory Syncytial Virus)

Wheezing or trouble breathing
Runny nose
Reduced appetite
Fever (occasionally)
Severe cough (in infants and older adults)

Allergies

Sneezing
Runny or congested nose
Itchy, watery eyes
Itchy throat
Postnasal drip
No fever or body aches

Determining the cause of a cough involves evaluating additional symptoms such as fever, nausea, and fatigue. While colds and allergies usually result in mild discomfort, conditions like flu, RSV, and COVID-19 might necessitate medical attention. If symptoms are severe, persistent, or worsen, it’s vital to consult a healthcare professional for an accurate diagnosis and treatment.

When to call the doctor?

Recognising when to seek medical help for respiratory ailments is essential to prevent complications. Although many instances of COVID-19, flu, colds, RSV, and allergies can be handled at home, certain symptoms indicate the necessity for professional intervention. Acknowledging these warning signs ensures timely treatment and a safer recovery.

COVID-19: Seek medical help for shortness of breath, chest pain, confusion, extreme fatigue, or bluish lips, as these could signal serious complications needing immediate care.
Flu: A high fever lasting more than three days, severe body aches, shortness of breath, or continuous vomiting may indicate complications and require immediate medical attention.
Common Cold: Consult a doctor if symptoms continue beyond ten days and feature intense sinus pain, facial pressure, or a lasting cough with wheezing, as these may suggest a secondary infection.
RSV: Medical assistance is necessary for rapid or laboured breathing, severe coughing, bluish lips, or signs of dehydration, especially in infants, older adults, or those with weakened immune systems.
Allergies: Urgent care should be sought if experiencing significant breathing difficulties, swelling of the face or throat, or persistent infections that do not improve with standard allergy treatments.

Understanding when to seek medical advice is critical in preventing complications arising from respiratory illnesses. While mild symptoms often resolve with home care, severe, enduring, or worsening symptoms require prompt medical evaluation for a suitable diagnosis and treatment.

When to consult a doctor for cold/flu/RSV

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Coughing stems from various illnesses, and although symptoms often overlap, you can differentiate between COVID-19, the flu, a cold, RSV, or allergies by observing the cough's nature and additional signs. For a precise diagnosis and proper treatment, especially when symptoms are severe or persistent, seeking advice from a healthcare professional is essential.

Reference

Whooping cough still lingers - reference link
United Nations Digital Library - reference link

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