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Allergy is a sensitivity to a specific substance called an allergen, which elicits a reaction and is usually contacted through skin, lungs, swallowing, or ingestion.

An allergic response is a collection of symptoms caused by an immune reaction to substances that do not trigger such a response in most people. The immune system normally protects the body against harmful substances such as bacteria, viruses and toxins.

Allergies occur when the immune system reacts to substances (allergens) that are generally harmless and in most people do not cause an immune response.

Kinds of Allergies
Various people report allergies ranging in a wide category from intolerance to dust, pollen to specific drugs. Here, we list a few of the common kinds of allergies.

Localized Itching: Skin irritation from insect bites and stings, chemical irritants, hives, parasites (lice. pinworms).

Common causes
Generalized: Dry skin. Childhood infections (such as chicken pox or measles), aging skin, allergy caused by food or drugs (antibiotics), pregnancy, hepatitis, iron deficiency anemia, pityriasis rosea, psoriasis, dermatitis, renal failure, urticaria, drugs such as antibiotics (penicillin, sulfonamides), gold, griseofulvin, ionized, opiates, phenothiazines, or Vitamin A.

The list of disorders which cause it is extensive and the exact cause can only be found out after detailed questioning. In addition certain skin lesions can be easily identified by the doctor e.g. seborrhic dermatitis, scabies, dry skin, hives etc.

Treatment for Pruritus
Medications are available to relieve itching. It must be emphasized that in addition to relieving itching, the underlying cause must be identified and treated by the health care provider. Moisturizers should be used for dry skin. Antihistamines are used orally when the itching is severe.

Allergic Rhinitis
Exposure to pollen, mold, dust and animal dander are some of the common environmental allergens. Allergy to environmental particles is a type of allergic rhinitis (Hay Fever).

Hay Fever usually involves an allergic reaction to pollen. However, people may develop an allergic reaction to other particles in the environment. The pollens that cause Allergic Rhinitis vary from person to person and from region to region.

In addition to individual sensitivity and regional plant prevalence, the amount of pollen in the air can be a factor in the development of Allergic Rhinitis symptoms. Hot, dry, windy days are more likely to have increased amounts of pollen in the air than cool, damp, rainy days where pollen is washed to the ground. Pollens that are carried by bees from plant to plant are seldom responsible for Allergic Rhinitis because the grains are large and have a waxy coating. Pollens that are carried by the wind are smaller and more often cause Allergic Rhinitis.

Common allergens for Allergic Rhinitis
Plants as allergens
Examples of plants commonly responsible for Allergic Rhinitis include: Ragweed, lowers, evergreen trees and grass. Many people are allergic to mold. Mold spores are carried in the air and may be present all year long. Mold is most prevalent indoors in damp locations and in swamp coolers, bathrooms, washrooms, fabrics, rugs, stuffed animals, books, wallpaper, and other “Organic” materials. Outdoors, mold lives in the soil, on compost, and on damp vegetation.

Dust is another common allergen. House dust contains microscopic particles of pollen, mold, fibers from clothing and other fabrics, detergents, and microscopic insects (mites). Mites, including small fragments of dead mites, are the primary causes of dust allergy.

Animals as allergens
Many people are allergic to animals. Most people are not allergic to the animal’s fur or feathers. They are actually allergic to the small scales of skin (dander) that the animal sheds. Some people are allergic to the animal’s saliva, particularly cats (whose saliva contains a protein known to cause allergy). Saliva exposure occurs if the animal licks the person. It may also occur from petting the animal after it has groomed itself or by touching an object that the animal has recently licked or chewed.

Environment as allergens
A few people develop allergies to other irritants in the environment, including smoke, fumes from industries or cleaning products, tobacco, powder (face powder, baby powder, and so on.), laundry detergents, and other common substances.

Food Allergies
Food allergies are often misunderstood. There is a great deal of general confusion about them, and they constitute a controversial area within the allergy field of medicine.

Often, what is at first thought to be a food allergy is found to be something else. For example, many people who think they are allergic to foods are merely sensitive to them. Others may have enzyme deficiencies which cause them to react adversely to a food in a non–allergic way. In the following article, these and other common misunderstandings about food allergies will be cleared.

The Classic Food Allergy
Let’s look first at “True” (or “Classic”) food allergies, and how to prevent and treat them. Classic food allergies include allergies to milk, soy, egg whites, shellfish and peanuts. Peanut allergy is a good example to examine, since it is one of the most widely known food allergies and is becoming more and more common. (It is also the food allergy most likely to be fatal). With classic food allergies, your body forms antibodies against the offending food. Even the smell of the food can cause a reaction in a highly allergic person. Peanut allergic persons do not like to eat snacks in planes where nuts are served.

Peanut Allergy
Why is peanut allergy becoming so much more prevalent?
The answer is simply that we are eating them more. Peanuts are healthy if you aren’t allergic to them, and as we adopt healthier lifestyles, we are incorporating them more often in one form or another into our diet.

One question frequently asked is whether or not people can outgrow their food allergies. The answer is both yes and no. While one sees this frequently with eggs and less commonly with dairy, nut allergies are rarely outgrown.

Diagnosis for Food Allergy
When someone has symptoms of a food allergy, it is important to note the time which elapsed between the consumption of the suspected food and the reaction. Food allergy reactions usually occur within minutes, and sometimes, within seconds. So, when a person says that he/she ate a certain food yesterday, some skin itching today is probably not due to a food allergy. Sometimes, a diagnosis can be made via trial and error, by eliminating a suspected food. If the skin clears up, the food is reintroduced to see if the skin flares up once more. If you are attempting such an elimination diet, stay off the offending foods for at least two weeks and add back each food one at a time every three days. {mospagebreak} The best diagnoses, for food allergies, however, are Skin Testing and RAST (blood) testing. In skin testing, the offending food is lightly scratched into the skin by a disposable plastic “Scratcher”. If you are allergic, the area gets red and itchy. The advantages are that the test results are ready within 20 minutes, and that it is cheaper than RAST tests.

RAST testing (which measures the presence of certain allergy–inducing antibodies in your bloodstream) is helpful where there is no specific allergy specialist who does skin testing. RAST testing is also useful as a confirmation of results from skin testing in individuals who have a rash on their back which would complicate a skin test or when only a couple of foods are suspected.

Managing food allergies
It is important to know what to do in case of accidental ingestion, which initially includes an over–the–counter antihistamine, such as diphenhydramine (Benadryl), if the reaction is not severe. In case of a severe attack, one should go to an emergency room. It is recommend that if they have a classic food allergy, they carry information about their allergy. If the allergic foods taste “Funny”, patients may try to leave a suspicious food in their mouth a few seconds before swallowing. The body’s natural desire to eliminate the problematic food by vomiting, can be lifesaving.

Prevention of Food Allergy
Food allergies are most easily developed when we are young. At this stage our intestines are not fully developed and allow large, complex proteins such as peanut protein to cross into the body. Our young bodies recognize such proteins as foreign and form antibodies against them. This may be why there is a great deal of milk allergy and soy allergy when those milks are fed to infants. To prevent peanut allergy, babies ideally should not get peanut protein at all during the first two or three years of life. It is advisable that pregnant women avoid peanuts, especially if there is a family history of food allergies or strong allergic reactions in general. They should also avoid peanut proteins when breast feeding. It may also be helpful to delay the introduction of some other foods (like other nuts, shellfish, milk, wheat, and soy) into an infant’s diet for the first six months of life, but this is a controversial issue. In the future, it is likely that there will be an oral or injected vaccine for peanuts, which will teach the body to become less allergic to it.

Drug Allergies
Some drugs (polymyxin, morphine, X–ray dye, and others) may cause an anaphylactoid reaction (anaphylactic–like reaction) on the first exposure. Anaphylactoid reaction is usually from a toxic or idiosyncratic reaction rather than the “Immune system” mechanism that occurs with “True” anaphylaxis.

Causes of drug allergies
Drug allergies occur when there is an allergic reaction to a medication. This is caused by hypersensitivity of the immune system, leading to a misdirected response against a substance that does not cause a response in most people. The body becomes sensitized (the immune system is triggered) by the first exposure to the medication. The second or subsequent exposure causes an immune response.

Drug reaction manifestations
Reactions to drugs are uncommon, but almost any drug can cause an adverse reaction. Reactions range from irritating or mild side–effects (such as nausea and vomiting), to allergic response including life–threatening anaphylaxis. Some drug reactions are idiosyncratic (unusual effects of the medication). For example, aspirin can cause non–allergic hives (no antibodies formed), or it may trigger asthma. “True” drug allergies involve the production of antibodies and the release of histamine and other chemicals. Most drug allergies cause minor skin rashes and hives. However, other symptoms occasionally develop and life–threatening, acute allergic reactions involving the whole body (anaphylaxis) can occur. Serum sickness is a delayed type of drug allergy that occurs a week or more after exposure to medication or vaccine. Penicillin and related antibiotics are the most common cause of drug allergies. Other common allergy causing drugs include sulfa drugs, barbiturates, anti–convulsants, insulin preparations (particularly animal sources of insulin), local anesthetics such as Novocain, and iodine (found in many X–ray contrast dyes).