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All You Need To Know About Allergies This Harmattan

OGUGUA BELONWU
6.22k views;
Posted on December 21, 2015;

Allergy Facts

  • Allergy involves an exaggerated response of the immune system, often to common substances such as foods or pollen.
  • The immune system is a complex system that normally defends the body against foreign invaders, such as bacteria and viruses, while also surveying for conditions such as cancer and autoimmunity.
  • Allergens are substances that are foreign to the body and that cause an allergic reaction.
  • IgE is the allergic antibody.
  • Although many individuals outgrow allergies over time, allergies can also develop at any age, including during adulthood.
  • While the environment plays a role in the development of allergy, there is a greater risk of developing allergic conditions if a person has a family history of allergy, especially in parents or siblings.

What is an allergy?

An allergy refers to an exaggerated reaction by the immune system in response to exposure to certain foreign substances. The response is exaggerated because these foreign substances are normally seen by the body as harmless in nonallergic individuals and do not cause a response in them. In allergic individuals, the body recognizes the foreign substance, and the allergic part of the immune system generates a response.

Allergy-producing substances are called "allergens." Examples of allergens include pollens, dust mites, molds, animal proteins, foods, and medications. When an allergic individual comes in contact with an allergen, the immune system mounts a response through the IgE antibody. People who are prone to allergies are said to be allergic or "atopic."

What causes allergies

A common scenario can help explain what causes allergies. A few months after the new cat arrives in the house, dad begins to have itchy eyes and episodes of sneezing. One of the three children develops coughing and wheezing. The mom and the other two children experience no reaction whatsoever despite the presence of the cat. How can this occur?

The immune system is the body's organized defense mechanism against foreign invaders, particularly infections. Its job is to recognize and react to these foreign substances, which are called antigens. Antigens often lead to an immune response through the production of antibodies, which are protective proteins that are specifically targeted against particular antigens. These antibodies, or immunoglobulins (IgG, IgM, and IgA), are protective and help destroy a foreign particle by attaching to its surface, thereby making it easier for other immune cells to destroy it. The allergic person however, develops a specific type of antibody called immunoglobulin E, or IgE, in response to certain normally harmless foreign substances, such as cat dander. Other antigens, such as bacteria, do not lead to production of IgE, and therefore do not cause allergic reactions. IgE was discovered and named in 1967 by Kimishige and Teriko Ishizaka.

Who is at risk

Allergies can develop at any age, but most food allergies begin at a young age, and many are outgrown. Environmental allergies can develop at any time. The initial exposure or sensitization period may even begin before birth. Individuals can also outgrow allergies over time. It is not fully understood why one person develops allergies and another does not, but there are several risk factors for allergic conditions. Family history, or genetics, plays a large role, with a higher risk for allergies if parents or siblings have allergies. There are numerous other risk factors for developing allergic conditions. Children born via Cesarean section have a higher risk of allergy as compared to children who are delivered vaginally. Exposure to tobacco smoke increases the risk of allergy. Boys are more likely to be allergic than girls. Allergies are more common in westernized countries, and less common in those with a farming lifestyle. Exposures to antigens, use of antibiotics, and numerous other factors, some of which are not yet known, also contribute to the development of allergies. This complicated process continues to be an area of medical research.

Parts of the body that are prone to allergic symptoms

The parts of the body that are prone to allergic symptoms include the eyes, nose, lungs, skin, and gastrointestinal tract. Although the various allergic diseases may appear different, they all result from an exaggerated immune response to foreign substances in sensitive individuals. The following are brief descriptions of common allergic disorders.

Some allergies include:

  1. Allergic Rhinitis (Hay Fever)
  2. Asthma
  3. Allergic eyes (conjunctivitis)
  4. Eczema
  5. Hives (urticaria)
  6. Allergic shock (anaphylaxis)

Where are the allergens?

Everywhere.

Allergens may be inhaled, ingested (eaten or swallowed), applied to the skin, or injected into the body either as a medication or inadvertently by an insect sting. The symptoms and conditions that result depend largely on the route of entry and level of exposure to the allergens. The chemical structure of allergens affects the route of exposure. Airborne pollens, for example, tend to have little effect on the skin. They are easily inhaled and will thus cause more nasal and respiratory symptoms with limited skin symptoms. When allergens are swallowed or injected, they may travel to other parts of the body and provoke symptoms that are remote from their point of entry. For example, allergens in foods may prompt the release of mediators in the skin and cause hives.

The specific protein structure is what determines the allergen's characteristics. Cat protein, Fel d 1, from the Felis domesticus (the domesticated cat), is the predominant cat allergen. Each allergen has a unique protein structure leading to its allergic characteristics.

In the air

Aside from oxygen, the air contains a wide variety of particles, including allergens. The usual diseases that result from airborne allergens are hay fever, asthma, and conjunctivitis. The following allergens can trigger allergic reactions when inhaled by sensitized individuals.

  • Pollens from trees, grasses, and/or weeds
  • Dust mites
  • Animal proteins, including dander, skin, and/or urine
  • Mold spores
  • Insect parts, especially from cockroaches

What we ingest

Foods and medications can also cause allergic reactions, some of which can be severe. These reactions often start with localized tingling or itching and then may lead to rash or additional symptoms, such as swelling, nausea, vomiting, diarrhea, or difficulty breathing. Here are the two most common allergens that are ingested:

  • Foods: The most common food allergens are cow's milk, eggs, peanuts, tree nuts, wheat, soy, shellfish, finned fish, and sesame. Cow's milk, egg, wheat, and soy allergies are most common in children and are often outgrown over time. The most common allergens in adults are peanut, tree nuts, and shellfish. It should be noted that gluten is not a common food allergy, and true gluten hypersensitivity, or celiac disease, is mediated by another type of antibody (not IgE but IgA) and also leads to a different host of symptoms (including chronic abdominal discomfort, nausea, vomiting, change in stool, anemia).
  • Medications: Although any medication can cause an allergic reaction, common examples include antibiotics (such as penicillin), and anti-inflammatory agents, such as aspirin and ibuprofen.

Touches our skin

Contact dermatitis is an inflammation of the skin that is caused by local exposure to a substance. The majority of these localized skin reactions do not involve IgE but are caused by other inflammatory cells. A good example is poison ivy. Examples of substances that commonly cause contact dermatitis include the following:

  • Plants (poison ivy, poison sumac, and poison oak)
  • Dyes
  • Chemicals
  • Nickel and other metals
  • Cosmetics

Injected into our bodies

The most severe reactions often occur when allergens are injected into the body and gain direct access to the bloodstream. This intravenous access carries the increased risk of a systemic reaction, such as anaphylaxis. The following are commonly injected allergens that can cause severe allergic reactions:

  • Insect venom
  • Medications
  • Vaccines (including immunotherapy [allergy shots])
  • Hormones (for example, insulin)

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