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What is the Common Cold?

What’s known as the “common cold” is, in fact, a group of mild, upper respiratory diseases caused by several different viruses. Colds are characterized by nasal congestion and discharge, sneezing, coughing, and sore throat. The illness mainly affects the upper respiratory tract (nose, throat, pharynx, and larynx) but can also spread to adjacent organs, resulting in more severe symptoms and susceptibility to bacterial infection.1

Common cold infections show a seasonal pattern. Cases of the common cold increase rapidly in the fall and decrease after winter, although sometimes a second peak is observed during spring. In tropical areas, most cold cases appear during the rainy season. On average, children have 6-8 episodes of colds per year, while adults only experience 2-4.1 About 25 million cases of the common cold are reported in the U.S. each year, causing absences from work and school.1,2

What are the symptoms?

Common cold symptoms are caused by an immune response to a viral infection of the upper airway. The most common symptoms of the disease, in order of appearance, are3:

  • Sore throat
  • Sneezing
  • Nasal discharge and congestion
  • Chills
  • Coughing

More severe symptoms of the common cold include fever (more common among children), muscle aches and pains, and mood changes.3

 What are the causes?

Different viruses cause the common cold. However, rhinoviruses and coronaviruses are the most frequent type of virus causing colds across all age groups.4 These viruses can be transmitted by1:

  1. Direct contact with an infected person or contaminated surface
  2. Small particles lingering in the air
  3. Direct exposure to virus containing particles from an infected person (if a person sneezes or coughs in front of you)

Once in the body, the virus enters the epithelial cells of the upper respiratory airways and rapidly replicates. The nasal mucosa responds by becoming inflamed, causing nasal obstruction and discharge. Mucus production increases, and sneezing begins.1

In regions with seasonal variations in temperature and humidity, winter is peak season for the common cold. A cold, dry environment and increased time spent indoors close to other people, both help spread viruses. The temperature of the human nose is lower in winter, which decreases local antiviral immune responses. This explains why it is easier for cold-causing viruses to replicate in winter – and why the infection usually starts in our nose.5 In contrast, in tropical climates where it is warm all year round, most rhinovirus infections occur at the start of the rainy season. Here, too, the spread of the viruses might be helped by increased time spent indoors with other people, and lower temperatures.6

Age is also an important risk factor, since children catch colds more often than adults. Other risk factors include1,7:

  • Genetics
  • Poor diet
  • Pre-existing immunodeficiency disorders or chronic diseases
  • Psychological stress
  • Smoking

How does this topic relate to my microbiome?

A direct relationship between the microbiota of the respiratory tract and the common cold has not yet been found. However, several studies suggest that the lung microbiota can help protect the body from certain respiratory diseases and infections. The microbiota can adjust to protect the respiratory tract against diseases and infections by strengthening the pulmonary barrier and boosting its immune response.8

Though they are not directly in contact, the gut microbiota can actually affect the immune functions of the lungs. Changes in either the gut or lung microbiota are associated with a higher risk of overall disease and more severe diseases.8

Which diseases/topics are related to common cold?

The common cold and influenza (or ‘the flu’) are very similar conditions. Because both appear during winter season and have very similar symptoms, they are often mistaken for one another. However, ‘the flu’ is caused by influenza viruses and has a rapid and sudden onset, more severe symptoms, and can involve headache, weakness, and loss of appetite.3

Other respiratory conditions, like common cold, include:

  • Bronchitis
  • Chronic obstructive pulmonary disease
  • Laryngitis
  • Pharyngitis
  • Pneumonia
  • Rhinosinusitis

How can I take action?

The best prevention is good hygiene, especially in children. During cold and flu season, you should wash your hands frequently with soap and water for at least 20 seconds, covering all surfaces of the hands and fingers. Alcohol-based hand sanitizers are also recommended when water and soap are not available. Stay away from people who are sick, and disinfect surfaces regularly to minimize contact with cold-causing viruses.2

Some other preventive measures with research support are:

  • Exercising 9
  • Getting at least 7-9 hours of sleep per night 10
  • Taking probiotics 11
  • Taking vitamin C12

If you have the common cold, you should stay at home to avoid spreading it to other people. If you have mild symptoms, you should rest and drink plenty of fluids. Over-the-counter medications – such as decongestants and antihistamines, which can reduce nasal congestion and discharge – may alleviate the most common symptoms.

Antibiotics will not help you recover since they are not effective against viruses. Antibiotics have no effect on reducing symptoms’ duration or severity, and only increase the risk of gastrointestinal distress and bacterial resistance.1,2,131,2,13

If your condition gets worse, the symptoms last more than 10 days, or you have a chronic disease – such as asthma, diabetes, or a heart disease – visit your healthcare provider to determine the best treatment for you.2


1. Heikkinen, T., & Järvinen, A. (2003). The common cold. The Lancet, 361(9351), 51–59.

2. Center for Disease Control and Prevention. Common Cold (2016).

3. Eccles, R. (2005). Understanding the symptoms of the common cold and influenza. Lancet Infectious Diseases, 5(11), 718–725.

4. Kirkpatrick, G. L. (1996). The common cold. Primary Care – Clinics in Office Practice, 23(4), 657–675.

5. Foxman, E. F., Storer, J.A., Fitzgerald, M. E., Wasik, B. R., Hou, L., Zhao, H., Turner, P. E., Pyle, A. M., and Iwasaki A. (2015). Temperature-dependent innate defense against the common cold virus limits viral replication at warm temperature in mouse airway cells. PNAS.

6. Winther, B. (2011). Rhinovirus Infections in the Upper Airway. Proceedings of the American Thoracic Society, 8(1):79-89.

7. Cohen, S., Tyrrell, D. A., Russell, M. A., Jarvis, M. J., & Smith, A. P. (1993). Smoking, alcohol consumption, and susceptibility to the common cold. American Journal of Public Health, 83(9), 1277–1283.

8. Hauptmann, M., & Schaible, U. E. (2016). Linking microbiota and respiratory disease. FEBS Letters, 590(21), 3721–3738.

9. Grande, A. J., Keogh, J., Hoffmann, T. C., Beller, E. M., & Del Mar, C. B. (2015). Exercise versus no exercise for the occurrence, severity and duration of acute respiratory infections. Cochrane Database of Systematic Reviews, 2015(6), CD010596.

10. Prather, A. A., Janicki-Deverts, D., Hall, M. H., & Cohen, S. (2015). Behaviorally Assessed Sleep and Susceptibility to the Common Cold. Sleep, 38(9), 1353–1359.

11. Hao, Q., Dong, B. R., & Wu, T. (2015). Probiotics for preventing acute upper respiratory tract infections. Cochrane Database of Systematic Reviews, 2015(2), CD006895.

12. Hemilä, H., & Chalker, E. (2013). Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews, 2013(1), CD000980.

13. Simasek, M., & Blandino, D. A. (2007). Treatment of the common cold. American Family Physician, 75(4).