The common cold is a viral infection of the lining of the nose, sinuses, and throat.
Common colds are among the most common illnesses. Many different viruses (rhinoviruses, adenoviruses, coronaviruses, and human metapneumoviruses) cause colds, but rhinoviruses (of which there are more than 100 subtypes) are implicated more often than others. Colds caused by rhinoviruses occur more commonly in the spring and fall. Other viruses cause common coldlike illnesses at other times of the year.
Colds spread mainly when people's hands come in contact with nasal secretions from an infected person. These secretions contain cold viruses. When people then touch their mouth, nose, or eyes, the viruses gain entry to the body and cause a cold. Less often, colds are spread when people breathe air containing droplets that were coughed or sneezed out by an infected person. A cold is most contagious during the first 1 or 2 days after symptoms develop.
Becoming chilled does not cause colds, nor does it increase a person's susceptibility to infection. General health and eating habits also do not seem to affect susceptibility to infection, nor does having an abnormality of the nose or throat (such as enlarged tonsils or adenoids).
Symptoms start 1 to 3 days after infection. Usually, the first symptom is a scratchy or sore throat or discomfort in the nose. Later, people start sneezing, have a runny nose, and feel mildly ill. Fever is not common, but a mild fever may occur at the beginning of the cold. At first, secretions from the nose are watery and clear and can be annoyingly plentiful, but eventually, they become thicker, opaque, yellow-green, and less plentiful. Many people also develop a mild cough. Symptoms usually disappear in 4 to 10 days, although the cough often lasts into the second week.
Complications may prolong the disease. Rhinovirus infection often triggers asthma attacks in people with asthma. Some people develop bacterial infections of the middle ear (otitis media) or sinuses. These infections develop because congestion in the nose blocks the normal drainage of those areas, allowing bacteria to grow in collections of blocked secretions.
Doctors are usually able to diagnose a cold based on the typical symptoms. A high fever, severe headache, rash, difficulty breathing, or chest pain suggests that the infection is not a simple cold.
Laboratory tests are not usually needed to diagnose a cold. If complications are suspected, doctors may order blood tests and x-rays.
Because so many different viruses cause colds and because each virus changes slightly over time, an effective vaccine has not yet been developed.
The best preventive measure is practicing good hygiene. Because many cold viruses are spread through contact with the secretions of an infected person, the following measures can help:
Despite their popularity, echinacea and high-dose vitamin C (up to 2,000 milligrams per day) do not prevent colds, nor does eating citrus fruits.
People with a cold should stay warm and comfortable and try to avoid spreading the infection to others. Anyone with a fever or severe symptoms should rest at home. Drinking fluids and inhaling steam or mist from a vaporizer have long been suggested as a way to help to keep secretions loose and easier to expel, but they probably help only a little bit.
Currently available antiviral drugs are not effective against colds. Antibiotics do not help people with colds, even when the nose or cough produces thick or colored mucus.
Echinacea (see Echinacea), zinc preparations (see Zinc), and vitamin C have been suggested as treatment. Some small studies have shown them to be effective. Others have shown them to be ineffective. But no well-designed, large clinical studies have confirmed their effectiveness. Even when studies did show a benefit, the benefit was small. For example, when zinc shortened the duration of cold symptoms, it was by less than 1 day. Thus, most experts do not recommend these supplements as treatment.
Several popular nonprescription (over-the-counter) remedies help relieve cold symptoms. Because they do not cure the infection, which usually resolves after a week regardless of treatments tried, doctors feel that their use is optional, depending on how bad the person feels. Several different types of drugs are used:
These drugs are most often sold as combinations but can also be obtained individually.
Inhaled decongestantsare better than forms taken by mouth for relieving nasal congestion. However, using inhaled forms for more than 3 to 5 days, then stopping, may make congestion worse than it was originally. Ipratropium, a nasal spray available only by prescription, helps dry a runny nose.
Older antihistamines, such as chlorpheniramine, can cause drowsiness. Newer antihistamines, such as loratadine, are less likely to cause drowsiness but are ineffective for treating the common cold.
Decongestants and antihistamines should not be given to children under 4 years old.
NSAIDs, such as aspirin, ibuprofen, and naproxen, can relieve aches and pains and reduce fever, as can acetaminophen. Aspirin is generally not recommended for children because in children, it increases the risk of Reye syndrome (see Reye Syndrome), which is a rare but life-threatening disorder.
Cough suppressants are not routinely recommended because coughing is a good way to clear secretions and debris from the airways during a viral infection. However, a severe cough that interferes with sleep or causes great discomfort can be treated with a cough suppressant.
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Last full review/revision December 2014 by Craig R. Pringle, BSc, PhD