Allergies are hypersensitivity reactions of the immune system to specific substances called allergens (such as pollen, stings, drugs, or food) that, in most people, result in no symptoms.

Allergies (Allergic Disease, Allergic Disorders, Allergic Illness)

Viennese pediatrician Baron Clemens von Pirquet coined the term “allergy” (from the Greek “allos” meaning changed or altered state and “ergon” meaning reaction or reactivity) in 1906. Von Pirquet used the term to describe an altered reaction he had observed in patients, which he put down to the influence of external factors, an allergen, on the immune system.

Allergies are hypersensitivity reactions of the immune system to specific substances called allergens (such as pollen, stings, drugs, or food) that, in most people, result in no symptoms.

The most severe form of allergy is Anaphylactic shock, which is a medical emergency.

Various types of classifications exist. Allergy has different names depending upon where in body it occurs.

Common Allergies:

  • Asthma
  • House Dust Mite Allergy
  • Food Allergy
  • Pet Allergy
  • Pollen Allergies
  • Insect Sting Allergy


Asthma can be defined clinically as a condition of intermittent, reversible airway constriction, due to a hyper-activity to certain substances producing inflammation.

In an asthma attack the smooth muscles of the lungs go into spasm with the surrounding tissue inflamed and secreting mucus into the airways. Thus, the diameter of the airways is reduced causing the characteristic wheezing as the person affected breathes harder to get air into the lungs. Attacks can vary in intensity and frequency.

Dust Mite, House Dust Mite

Dust mites are microscopic organisms found in homes and are the primary cause of allergies related to dust. It is actually the excretion of these mites to which people are allergic. Therefore, dust mites can cause allergic reactions even when dead.

Food Allergy

A food allergy is any adverse reaction to a food or food component involving the body’s immune system. Some adverse reactions to foods do not involve the immune system and are known as food intolerance, e.g. food poisoning or the inability to properly digest certain food components such as lactose or gliadin.

A true allergic reaction to a food involves two primary components:

Contact with food allergens (part of the food that stimulates the immune system);

Immunoglobulin E (IgE: an antibody in the immune system that reacts with allergens) and mast cells (tissue cells) as well as basophils (blood cells), which release histamine or other substances causing allergic symptoms when IgE antibodies attach onto these cells.

Although most Americans consume a wide variety of food additives daily, only a small number have been associated with reactions. These reactions do not involve the immune system and therefore are examples of food intolerance rather than food allergy.

While most allergic reactions to food are relatively mild, a small percentage of food-allergic individuals have severe reactions that can be life threatening. Anaphylaxis is a rare but potentially fatal condition in which several different parts of the body experience food-allergic reactions simultaneously, causing hives, swelling of the throat and difficulty in breathing.

Food allergies can cause a host of symptoms, including: swelling of the lips; tongue or throat; hoarseness; cough; hives; skin rashes; a runny nose and watering eyes; and asthma. Sometimes symptoms are limited to nausea, vomiting, or cramping diarrhea. Symptoms of a food allergy are highly individualistic and usually begin within minutes to a few hours after having eaten the offending food.

The most common food allergens involved in food allergy are shellfish, milk, fish, soy, wheat, peanuts, egg and tree nuts such as walnuts. Pharmacologically active substances found in food include histamine, tyramine, tryptamine and serotonin, which may be consumed in foods such as red wine, cheese, yeast extract, avocados and bananas. In susceptible people, these foods can trigger urticaria , facial flushing and headaches. Patients with hypersensitivity to avocados, bananas, kiwis or chestnuts sometimes exhibit clinical reactions to latex. This is termed Cross-Reactivity.

There are a variety of forms in which food hypersensitivity expresses itself. These include:

Oral Allergy Syndrome

Food Intolerance

Gastrointestinal disease with an immunologic basis, e.g. Chronic Ulcerative Colon; Celiac Disease; Crohn’s Disease.

Pet Allergy

Many people are allergic to animals. Most people are not allergic to the animal’s fur or feathers. The allergy is more usually an immune reaction to a protein (an allergen) found in the saliva, dander (dead skin flakes) or the urine of an animal. The allergen gets carried in the air or in dust on very small, invisible particles. It then lands on the lining of the eyes (conjunctiva) and nose. It may also be inhaled directly into the lungs, causing allergic symptoms. Allergen contact with an allergic person’s skin may also cause itching and hives.

Pollen Allergy

A hypersensitive reaction to pollen. While grass pollens are generally the most common cause of hay fever (seasonal allergic rhinitis), other pollen types are also important. These include tree pollens such as alder, hazel, birch, beech, cypress, pine, chestnut and poplar, and weed pollens such as plantain and ragweed. The relative importance of the kinds of pollen that can cause hay fever varies between different climatic and vegetation zones. For example, ragweed pollen, although very common in North America, is present in Europe only in the French Rhône valley and some areas of Eastern Europe, while the pollen most associated with seasonal allergy in Mediterranean regions is the olive tree. A person allergic to one pollen is generally also allergic to members of the same group or family (e.g. Betulaceae). Pollen induced reactions include extrinsic asthma, rhinitis and bronchitis.

Insect Sting Allergy

Insect Sting Anaphylaxis

Allergic reactions to insect stings can be so severe that death may occur within the few minutes following a sting. Even if not fatal, sting allergy symptoms can be frightening, including dizziness, itchy welts or massive swelling of the body, inability to breathe, swallow or speak, fainting from low blood pressure and shock.

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