 Allergy: What is it?
The term allergy is used to describe a response, within the body, to a substance, which is not necessarily harmful in itself, but results in an immune response and a reaction that causes symptoms and disease in a predisposed person, which in turn can cause inconvenience, or a great deal of misery.
An allergy is your body's reaction to a foreign substance - such as pollen or pet dander - that enters, or comes in contact with the body. It may be that pollen never bothered you before but over time, and with repeated exposures, your body grew overly sensitive to it, resulting in allergy symptoms such as sneezing and watery eyes. When foreign substances such as pollen cause allergic reactions, they are called allergens.
Allergens cause cells in your body to release chemicals known as mediators, which trigger allergy symptoms. These mediators include histamine and prostaglandins.
- Histamine is the mediator that stimulates mucus production and causes redness, swelling and inflammation.
- Prostaglandins are mediators that constrict airways and enlarge blood vessels.
Almost anything can be an allergen; the most common being house dust mites, pollen from trees and grasses, cats, dogs, insects such as wasps and bees, milk, eggs, peanuts. Less common allergens include nuts, fruit and latex. Protein is often regarded as just something that we eat. It is, in fact, an organic compound containing hydrogen, oxygen and nitrogen, which form an important part of living organisms. There are, however, some non-protein allergens which include penicillin and some other drugs. For these to cause an allergic response they need to be bound to a protein once they are in the body.
Allergic reactions or diseases may involve any part of the body; the most frequently involved are the nose and chest with resultant symptoms of hay fever, rhinitis or asthma, respectively. The skin and eyes also commonly show allergic symptoms. Anaphylactic shock is a severe allergy, which affects many organs at the same time causing a rapid decrease in blood pressure, fainting and, occasionally, death. Such a reaction, though, is rare.
If you suffer from hay fever, the pollens of grasses, weeds and trees are the main causes of this type of allergy, although mold spores can also cause the symptoms.
In perennial allergic rhinitis, the symptoms are similar to hay fever but appear all the year round. This condition is caused by non-seasonal allergens such as house dust components and certain molds.
The stomach and the digestive system are also frequent targets for allergic disease. Your symptoms are caused by allergy to foods, which can result in vomiting, stomach pains, diarrhea or constipation. Frequently, eczema and hives may be produced after ingesting food to which you are allergic. Food allergy may also trigger asthmatic attacks and, rarely, generalized anaphylaxis. Food anaphylaxis is most commonly seen with ingestion of nuts and iodinated shellfish (lobster, shrimp).
The term occupational allergy is generally used to describe episodes of allergic reactions occurring after working with industrial dusts, vapors, gases or fumes. Furthermore, substances like nickel (in coins), chromium (in cement), rubber, different dyes, formaldehyde and glues may result in eczema that occurs at the site of contact with the skin. Inhalants such as grain dust may affect farmers.
The degree of eczema depends on the length of exposure and sensitivity to the substance. Symptoms may show within some weeks - but it can often take months, years, sometimes decades, before an eczema develops. Any part of the skin may become affected, but the most frequent sites are the hands, arms and the face, because these tend to be the least protected parts of the body. Occupational allergy may also present with pulmonary or upper respiratory treatments.
Severe allergic reactions to bee and wasp stings are not uncommon. More people die annually in the United States from insect sting allergy than die from snakebite. The local toxic reaction and discomfort that usually occurs following an insect sting is not generally considered to be allergic.
If you have had a severe insect sting or allergic reaction, your clinician may provide you with an adrenaline containing kit for use if you are stung. Should you be highly sensitive to bee or wasp stings, you may become unconscious within a short space of time. Immediate action should be taken to get you expert medical treatment, preferably at the nearest hospital.
IgE mediated (allergic) reactions induce symptoms such as nettlerash (urticaria, hives), running nose and eyes, swelling of the throat, attacks of asthma and, in severe cases, fainting. Swelling of an entire extremity is called a "large local reaction." Although indicative of hypersensitivity, this type of reaction does not, generally, proceed to anaphylaxis with future stings.
Allergy is an unusual reaction or sensitivity to substances that do not bother most people.
Following exposure to common environmental allergens, the allergic individual produces a special type of antibody, called Immunoglobulin E, or IgE. The healthy individual has a very low level of IgE in the blood, while those with certain allergic conditions such as hay fever, allergic asthma and some forms of eczema have high IgE levels. People with eczema have especially high blood levels of IgE.
In the human body, certain cells called mast cells and basophils are involved in allergic reactions.
IgE, produced as a result of repeated allergenic stimulation, attaches to the surface of these cells and subsequent binding of the allergen punctures the cell wall, leading to the release of different substances.
Anyone can develop an allergy, but the probability is increased if one or both parents suffer from some kind of allergic condition. Indeed, the presence of another allergic individual in the family is the strongest factor for predicting allergy in a child. It must be noted, though, that even when both parents are affected, a child may not be. Conversely, allergic children are born to normal parents and in such cases other factors, such as infection, may be responsible for the development of the allergy. Repeated exposure to a substance is required before the body can recognize it as foreign and mount an allergic response.
If you are allergic to house dust, your home should be vacuum-cleaned daily, especially the bedroom; this cleaning should be done by someone who is not allergic, if possible.
Fitted carpets and dust-collecting furniture should be avoided. Bedrooms should be kept as dust free as possible. Mattresses and pillows are best made of synthetic material. Feather pillows and down comforters should be avoided. Allergy to house dust might be similar to or the same as allergy to house dust mites, which are microscopic creatures living in bedding and carpets.
In theory, one way to avoid an allergen is to move to another location where the plant responsible does not grow. This is not always practical, however, since there might be a need to change jobs, school, friends, etc.; and besides, the person with a pollen allergy may very well become allergic to different pollens in his/her new location.
It is useful to keep bedroom windows closed to prevent the wind bringing in pollens. It is also advisable to air bed linen in the morning when the pollen count is at its lowest. When there is a lot of pollen in the air (e.g., hot, windy, dry day), it may be necessary to stay indoors with the doors and windows closed.
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