What is the difference between Hay Fever and common cold?
Posted by cedley1969
hay fever is caused by allergens, pollen etc. a cold is an infection caused by a virus.
Posted by hotirongirl
Hay Fever is caused by allergens in the air
Common cold is caused by a virus/bacteria
Posted by bocoo_man
Hay fever is caused by a multitude of pollens. The common cold is caused by a cold germ. You never get the same cold twice. There are so many different ones that you will never have them all. Hay fever is not treated with cold medicines. By by antihistamines or allergy med.
Posted by allyally14
Hayfever:
Seasonal allergic rhinitis, also called pollinosis, hay fever or nasal allergies, and often also written together as hayfever, is a collection of symptoms, predominantly in the nose and eyes, that occur after exposure to airborne particles of dust, dander, or the pollens of certain seasonal plants in people who are allergic to these substances.
When these symptoms are caused by pollens, the allergic rhinitis is commonly known as "hay fever", after the fact it is most prevalent during haying season.
Causes
Allergies are caused by an oversensitive immune system, leading to a misdirected immune response. The immune system normally protects the body against harmful substances such as bacteria and viruses. Allergy occurs when the immune system reacts to substances (allergens) that are generally harmless and in most people do not cause an immune response.
As noted above, hay fever involves an allergic reaction to pollen. A virtually identical reaction occurs with allergy to mold, animal dander, dust, and similar inhaled allergens. Particulate matter in polluted air and chemicals such as chlorine and detergents, which can normally be tolerated, can greatly aggravate the condition.
The pollens that cause hay fever vary from person to person and from region to region; generally speaking, the tiny, hardly visible pollens of wind-pollinated plants are the predominant culprits. Pollens of insect-pollinated plants are too large to remain airborne and pose no risk. Examples of plants commonly responsible for hay fever include:
Trees: such as birch (Betula), alder (Alnus), hazel (Corylus), hornbeam (Carpinus), horse chestnut (Aesculus), willow (Salix), poplar (Populus), plane (Platanus), linden/lime (Tilia) and olive (Olea). In northern latitudes birch is considered to be the most important allergenic tree pollen, with an estimated 15-20% of hay fever sufferers sensitive to birch pollen grains. Olive pollen is more important in Mediterranean regions.
Grasses (Family Poaceae): especially rye (Lolium sp.) and timothy (Phleum pratense). An estimated 90% of hay fever sufferers are allergic to grass pollen.
Weeds:ragweed (Ambrosia), plantain (Plantago), nettle/parietaria (Urticaceae), mugwort (Artemisia), Fat hen (Chenopodium) and sorrel/dock (Rumex)
In addition to individual sensitivity and geographic differences in local plant populations, the amount of pollen in the air can be a factor in whether hay fever symptoms develop. Hot, dry, windy days are more likely to have increased amounts of pollen in the air than cool, damp, rainy days when most pollen is washed to the ground.
The time of year at which hay fever symptoms manifest themselves varies greatly depending on the types of pollen to which an allergic reaction is produced. As most pollens are produced at fixed periods in the year, a long-term hay fever sufferer may also be able to anticipate when the symptoms are most likely to begin and end, although this may be complicated by an allergy to dust particles.
When an allergen such as pollen or dust is inhaled by a person with a sensitized immune system, it triggers antibody production. These antibodies bind to cells that contain histamine. When the antibodies are stimulated by pollen and dust, histamine (and other chemicals) are released. This causes itching, swelling, and mucus production. Symptoms vary in severity from person to person. Very sensitive individuals can experience hives or other rashes.
Some disorders may be associated with allergies. These include eczema and asthma, among others.
Allergies are common. Heredity and environmental exposures may contribute to a predisposition to allergies.
Symptoms
coughing
headache
itching nose, mouth, eyes, throat, skin, or any area
runny nose (and occasionally nosebleeds)
impaired smell
sneezing
stuffy nose (nasal congestion)
tearing eyes
sore throat
wheezing
cross-reactivity allergy to certain fruits
Common Cold:
Acute nasopharyngitis, often known as the common cold, is a mild viral infectious disease of the the upper respiratory system (nose and throat). Symptoms include sneezing, sniffling, nasal congestion; scratchy, sore, or phlegmy throat; coughing; headache; and fatigue. Colds typically last three to five days, with residual coughing lasting up to three weeks. As its name suggests, it is the most common of all human diseases, infecting subjects at an average rate of slightly over one infection per year per person. Infection rates greater than three infections per year per person are not uncommon in some populations. Children and their caretakers are at a higher risk, probably due to the high population density of schools and the fact that transmission to family members is highly efficient.
The common cold belongs to the upper respiratory tract infections. It is different from influenza, a more severe viral infection of the respiratory tract that shows the additional symptoms of rapidly rising fever, chills, and body and muscle aches. While the common cold itself is rarely life threatening, its complications, such as pneumonia, can very well be.
The common cold is caused by numerous viruses (mainly rhinoviruses, coronaviruses, and also certain echoviruses, paramyxoviruses, 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. Because of this, "curing the common cold" is a common metaphor for a desirable but likely impossible result. The nasopharynx is the central area infected. The reasons that the virus concentrates in the nasopharynx rather than the throat may be the low temperature and high concentration of cells with receptors needed by the virus.
Transmission
The viruses are transmitted from person to person by droplets from coughs or sneezes. The droplets or droplet nuclei are either inhaled directly, or 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 or eyes.
The virus takes advantage of sneezes and coughs to infect the next person before it is defeated by the body's immune system. Sneezes expel a significantly larger concentration of virus "cloud" than coughing. The "cloud" is partly invisible and falls at a rate slow enough to last for hours—with part of the water droplets evaporating and leaving much smaller and invisible "droplet nuclei" in the air. Droplets from turbulent sneezing or coughing or hand contact also can last for hours on surfaces, although less virus can be recovered from porous surfaces such as wood or paper towel than non-porous surfaces such as a metal bar. A sufferer is most infectious within the first three days of the illness. Symptoms, however, are not necessary for viral shedding or transmission, as a percentage of asymptomatic subjects exhibit viruses in nasal swabs, likely controlling the virus at concentrations too low for them to have symptoms.
Mechanism of Infection
The virus enters the cells of the lining of the nasopharynx (the area between the nose and throat), and rapidly multiplies. The major entry points are the nose and eyes, through the nasolacrymal duct drainage into the nasopharynx. The mouth is not a major point of entry and transmission does not usually occur with kissing or swallowing.
The virus enters the cell by binding to ICAM-1 receptors in these cells. The presence of ICAM-1 affects whether a cell will be infected. Its concentration also can be affected by various other factors, including allergic rhinitis and some other irritants including rhinoviruses themselves. ICAM-1 has been a major focal point in drug research into cold treatments.
Symptoms
Ninety-five percent of people exposed to a cold virus become infected, although only 75% show symptoms. The symptoms start 1–2 days after infection. Generally a cold starts with a sore throat, without any respiratory blockage. From then onwards the symptoms 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.
After a common cold, a sufferer develops immunity to the particular virus encountered. However, because of the large number of different cold viruses, this immunity offers limited protection. A person therefore can be easily infected by another cold virus, starting the process all over again.
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