The common cold is caused by
numerous viruses (mainly rhinoviruses, coronaviruses and also certain echoviruses
and coxsackieviruses) infecting the upper respiratory system. Several
hundred cold causing viruses have been described, and a virus can mutate to
survive, ensuring that any cure is still a long way off if not impossible.
These are transmitted from person to person by droplets resulting from
coughs or sneezes. The droplets are either inhaled directly, or, more
commonly, transmitted from hand to hand via handshakes or objects such as
door knobs, and then introduced to the nasal passages when the hand touches
the nose, mouth or eyes.
The virus enters the cells of
the lining of the nose and throat, and rapidly multiplies inside them.
Seventy-five percent of people exposed to a cold virus become infected with
symptoms. The symptoms start 1-2 days after infection. They are a result of
the body's defense mechanisms: sneezes, runny nose and coughs to expel the
invader, and inflammation to attract and activate immune cells. The virus
takes advantage of sneezes and coughs to infect the next person before it
is killed by the body's immune system. A sufferer is most infectious within
the first three days of the illness.
After a common cold, a
sufferer develops immunity to the particular virus encountered. Because of
the large number of different cold viruses however, this immunity is of
limited use and a person can easily be infected by another cold virus to
start the process all over again.
The term "cold" is
misleading, if "cold" refers to climatic temperature, as the
temperature does not appear to play a role, nor are any other factors known
which affect the probability of infection. A person can best avoid colds by
avoiding those who are ill and objects they touch, as well as keeping their
immune system in top form by getting enough sleep, eating nutritious foods,
and avoiding alcohol consumption. It is perhaps the case that
"cold" refers to a "cold condition," i.e., the hot,
cold, dry and wet "conditions" described by the ancient Roman
physician Galen. Colds are somewhat more common in winter since during that
time of the year people spend more time indoor in close proximity of others
and ventilation is less, increasing the infection risk. Weak health or
other allergies can be aggravated due to infection.
Bacteria that are normally
present in the respiratory tract can take advantage of the weakened immune
system during a common cold and produce a co-infection. Bacterial sinusitis
is a common coinfection. A possible explanation for these coinfections is
that strong blowing of the nose drives nasal fluids into those areas.
The best way to avoid a cold
is to avoid close contact with existing sufferers, to wash hands regularly(anti-bacterial
soaps have no effect), and to avoid touching the face. In some countries,
such as Japan, people with the common cold wear surgical masks. Because of
the large variety of viruses causing the common cold, vaccination is
There is no cure for the
common cold, i.e. there is no treatment that directly fights the virus.
Only the body's immune system can effectively destroy the invader. A cold
may be composed of several million viral particles, and typically within a
few days the body begins mass producing a better tailored antibody that can
prevent the virus from infecting cells, as well as white blood cells which
destroy the virus and destroy infected cells to prevent further viral
therefore focus on relieving the symptoms.
For some people, even without
these remedies, colds are relatively minor inconveniences and they can go
on with their daily activities with tolerable discomfort. This discomfort
has to be weighed against the price and possible side effects of the
remedies, and the possibility, not yet scientifically proven, that by
suppressing responses evolved to fight the cold, the symptom supressants
may prolong the illness.
Common treatments include:
analgesics such as NSAIDs such as aspirin or acetaminophen as well as
localised versions targeting the throat (often delivered in lozenge form),
nasal decongestants which reduce the inflammation in the nasal passages by
constricting local blood vessels, cough suppressants (which work like a
narcotic to suppress the cough reflex of the brain or by diluting the mucus
in the lungs), and first generation anti-histamines such as
brompheniramine, chlorpheniramine, and clemastine (which reduce mucus gland
secretion and thus combat blocked/runny noses but also may make the user
drowsy). Second generation anti-histamines do not have a useful effect on
A warm and humid environment
and drinking lots of hot fluids alleviate symptoms somewhat. Common home
remedies include camomile tea, chicken soup, medicinal mixtures, hot
compresses, hot toddies, vitamin C, although despite several scientific
trials there is no evidence that the final two have a beneficial effect.
Hot beer is also recommended, and though it does little to fight the
infection directly, at least it can help to a good night of relaxed sleep.
Zinc-nasal sprays claim
clinical proof that they work. The trick seems to be threefold.
1-The treatment has to be a
2-Treatment should be started
at the first sign of a cold before it has the chance to get established.
3-The type of zinc must be
zinc gluconate usually labelled as zincum gluconicum.
Antibiotics are ineffective
against the common cold and all other viral infections. They are useful in
treating any secondary bacterial infections that sometimes occur, but
treatment with antibiotics before these coinfections develop is
counterproductive, as it produces drug resistance, and can even promote
infections by killing off normal bodily flora.
Colds were known in ancient
Egypt; there were hieroglyphs for cough and for the common cold. The Greek
Hippocrates gave a description of the disease in the 5th century BC.
In the 18th century, John
Wesley wrote a book about curing diseases; it advised cold baths as
prevention and stated that chilling causes the common cold. The work was
widely reprinted in the 19th century. Another book by William Buchan in the
18th century also gave wet feet and clothes as the cause of the common
The idea of microscopic
infectious agents causing disease arose in the second half of the 19th
century. Initially, bacteria were suspected to be the cause of the common
cold, and vaccines were produced based on this theory; these were still
prescribed in the 1950s.
Viruses had been described
beginning with the 1890s: infectious agents so small that they could pass
through all filters and could not be seen under a microscope. In 1914,
Walter Kruse, a professor in Leipzig, showed that viruses caused the common
cold: nose secretions of a cold sufferer were diluted, filtered, and
introduced into the noses of volunteers, producing colds in about half of
the cases. These findings were not widely accepted, until Alphonse Dochez
repeated them in the 1920s, first in chimpanzees, and then in human
volunteers using a proper double-blind setup.
Among laymen, the common
assumption that cold or wet clothes or feet cause the common cold persists
to this day.
In Britain, the civilian
Medical Research Council set up the Common Cold Unit in 1946. The unit
worked with volunteers who were infected with various viruses. The
rhinoviruses were discovered there. In the late 1950s, it was shown how to
grow these cold viruses in tissue culture. In the 1970s, it was also shown
that treatment with interferon during the incubation phase of rhinovirus
infection protects somewhat against the disease, but no practical treatment
could be developed. The unit was closed in 1989.
Beginning in the 1960s, Nobel
Prize winner Linus Pauling heavily advocated the intake of large doses of
Vitamin C to prevent infection. In 1970 he wrote the bestseller Vitamin C
and the Common Cold. However, several subsequent studies have shown that
the vitamin does not have a protective effect against the common cold.