Interesting question. Thanks for asking.
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In short, I am not a doctor. My research did turn up the following
discussions on the subject of mucous and the common cold, and it does
not appear that there is total agreement in the medical community.
One of the better brief descriptions of mucous and the common cold
that I found is on a page from the Eastern Virginia Medical School:
"...The symptoms of the common cold consist primarily of runny nose,
nasal congestion, cough, and low grade fever (usually less than
102.2°F). In addition, occasional sneezing, mild aches, chills, and a
scratchy throat may occur. Initially, the nasal drainage is clear and
watery, but it becomes thickened and colored over the first few days
of illness. This color change represents an increase in the infection
fighting cells (or white blood cells) in the area and does not
necessarily signify the development of bacterial sinusitis. Most of
these symptoms should peak during the first one to three days of the
illness and gradually get better in up to 10 to 14 days..."
And then the Medical University of South Carolina mentions:
"...Another misconception that we hear frequently is that the color of
the mucous associated with the cold defines viral verses bacterial
infection. This is in fact not the case. A person will go from clear
to yellow to green mucous during the duration of the 7-10 days of a
cold. Studies have shown that the color of mucous plays no active role
in defining virus or bacteria..."
Shenandoah University notes the following:
"...Cold viruses provoke a massive immune response (sneezing,
inflammation, secretions, and so forth), including an increase in
certain types of immune cells that, in the course of recovery, may add
yellow or greenish color to the discharge..."
Which would lead me to believe that this is indication of imminent
recovery, yet Your Pure Life in the UK says:
"...Rhinovirus is the primary cause of the common cold or flu.
Documented evidence reveals 80% of all colds, sickness and disease
enter the body through the nasal passages. During a virus infection,
the nose has poor resistance against bacterial infections, which
explains why bacterial infections of the nose and sinuses so often
follow a "cold." When the nasal mucus turns from clear to yellow or
green, it usually means that a bacterial infection has taken over and
a physician should be consulted..."
Indicating to me that they believe color change is indicative of
increased severity. As you can see, there appear to be differing
opinions as to the presence of color indicating healing and recovery
or a move from viral inspired to bacterial infection.
And then, The Texas Medical Center reports:
"...Your child is sick with a slight fever, strong cough, and
discolored mucous. Does he need an antibiotic? Your doctor can tell
you for sure, but chances are good that he does not. As a matter of
fact, because many children are given antibiotics unnecessarily, a
major problem is spreading across Texas...
..."Many parents don't know, for example, that discolored mucous is
not a sign of a bacterial infection. It's normal for mucous to be
clear at the beginning of a cold, then discolored, then clear. A
common cold (and the discolored mucous associated with it) will go
away on its own."..."
A cached page from Penn State on Cold Assessment -
notes that colored mucous for more than 5 days should require looking
into by a medical professional. And then, Whole Health MD offers a
different time frame:
"...If cold symptoms last for more than 10 days, especially if they
get worse. You should see a doctor if you develop a productive
bronchial cough, sinus congestion and pain (especially if your mucous
discharge turns yellow or brown or green in color..."
Confusing? It is to me.
An herbal remedy page has a good definition of the common cold:
"...The common cold is an infection of the upper respiratory tract
caused by a virus. Cold weather does not cause colds, although most
colds are caught in the fall and winter. This is because most cold
viruses thrive better in colder temperatures, when there is less
humidity in the atmosphere. There are over 200 viruses that can cause
the common cold, an infection of the upper respiratory tract, but the
most common ones are rhinoviruses. The well-known symptoms include
head congestion, nasal congestion, sore throat, coughing, headache,
sneezing, and water eyes. Children may develop a low-grade fever, but
this is rare in adults. Colds usually strike eighteen to twenty-four
hours after the virus enters the body. Most colds clear up on their
own in a week to ten days, but occasionally a cold can lead to a more
serious illness, such as bronchitis, a middle ear infection, or sinus
infection. There is often confusion between the symptoms of the common
cold, influenza, and allergies. Influenza, also a viral respiratory
infection but caused by different types of viruses, is by far the most
serious complaint of the three and can lead to life-threatening
complications, particularly in older or frail people.
Healthy adults get an average of two colds per year. Children
generally get many more because their immune systems are immature and
they have not yet developed immunity to many of the viruses that cause
She mentions mucous color in diagnosing for the following herbal remedy treatments:
...Pulsatilla is indicated when the mucous has become thick and
yellow-green. A fluent discharge may alternate with nasal congestion.
The nose tends to run in the open air and in the evening and becomes
stuffed up in a warm room. Pulsatilla matches both dry and loose
coughs. The cough will often wake the person during the night...
...Rhus tox symptoms usually include a congested nose with a thick,
yellow or green discharge, a red and scratchy throat, and a dry cough
with tickling behind the upper part of the breastbone. Hoarseness is
common. The cough worsens in cold rooms, wet weather, after bathing,
and at night. In general, the person is restless and feels better when
A more technical and extensive description of the common cold can been
found at MoonDragon, another herbal remedy site:
Now, the University of Missouri provides a chart to aid in determining
the severity of symptoms:
IS IT A COLD, THE FLU OR PNEUMONIA?
An yet, the only mention of color and thickness of mucous here points
...Severe cough & stabbing chest pain *** ( Difficult painful
breathing and a cough with thick rust, green or yellow mucus are
common signs.)... is under the Bronchial Pneumonia column.
At Florida Ear and Sinus, they seem to adopt the middle ground on time
frame of color and thickness changes:
"...When a cold lasts more than a week and the mucus turns
yellow/green or develops a bad odor or taste, then a bacterial
infection has probably taken over..."
Health Education Associates details the color progression as relates to Bronchitis:
"...when the bronchial passages (also referred to as the
tracheobronchial tree) initially become irritated and then inflamed,
there is frequently swelling and increased mucous production. When
this happens, the area is often immediately invaded by white blood
cells. As cells that line the bronchial passages die they are shed
into the bronchial tubes along with a watery to thick sticky mucous
which is generally produced in response to the irritation. Initially,
this is a reaction to inflammation helps to keep the bronchial
passages clean. However as the mucous becomes thicker and stickier its
cleansing capacity is reduced and the ability of the bronchi to
function normally is disturbed. When this happens bacteria can invade
the compromised tissues and the normally sterile bronchi become
infected. When the bronchial tubes are not infected, the mucous
produced is usually clear and white in color. As infection increases,
there is cellular shedding and mucous production also increases. As
mucous production increases the progressively thickened mucous becomes
mixed with shedding cells, white blood cells, primary or secondary
bacteria's and/or viruses. As more and more of the cells that line the
bronchial tubes die and shed, the mucous becomes thicker and more
opaque. As elements of infection are mixed in the mucous turns yellow
and then as infection builds turns to a light greenish color and then
if the process continues to it may become darker and darker green.
When mixed with red blood cells from severe infection the mucous will
turn eventually turns to a brownish color or even bloody in nature.
As the mucous production increases, coughing develops. While this
cough, may only be slightly distressing in the beginning, it is
essential for it helps the body to eliminate the excess bronchial
secretions. Generally, most people will tolerate some coughing but if
the coughing progresses to the point that it begins to become
uncomfortable they will often go to their neighborhood drug store for
some sort of cough medication. Those medications which help to liquefy
the mucous are most beneficial as they generally loosen the mucous and
make it easier to bring up. This will initially reduce the effort it
takes to cough and make the cough more tolerable..."
As I continued to search, I started to build some consensus that most
usually, when accompanied by the other Common Cold signs, colored and
thickened mucous indicates that the cause is viral, is normal, shows
that white blood cells are being killed and healing is occurring. The
mucous will return to clear as healing progresses.
Depending on your choice of expert, if this does not clear for a
period of time between 5 and 10 days, then a professional medical
opinion is advised, particularly to see if the problems have moved
from viral based to bacterial. In the "normal" progression of the
Common Cold, mucous will turn from clear, to thick and colored and
back to clear. The median seems to say if colored persists for more
than a week, it should be checked further.
So, the length of time for discoloration plus the combination of other
symptoms such as fever, coughs and aches help to diagnose whether the
mucous color indicates a recovery period from a cold or a bacterial
onset of something perhaps more serious.
mucous +"common cold" +color
mucous +color OR thickness +healing OR recovery
"common cold" +mucous +color OR thickness
I trust my research has been helpful in answering this question. If a
link above should fail to work or anything require further explanation
or research, please do post a Request for Clarification prior to
rating the answer and closing the question and I will be pleased to