What are Allergies?

Allergies are abnormal reactions of the immune system which occur in response to otherwise harmless substances.

An allergy is a type of immune reaction. Normally, the immune system responds to foreign microorganisms or particles, like pollen or dust, by producing specific proteins called antibodies that are capable of binding to identifying molecules, or antigens, on the foreign particle. This reaction between antibody and antigen sets off a series of reactions designed to protect the body from infection. Sometimes, this same series of reactions is triggered by harmless, everyday substances. This is the condition known as allergy, and the offending substance is called an allergen.

Allergens enter the body through four main routes…

The airways, the skin, the gastrointestinal tract, and the circulatory system.

People with allergies are not equally sensitive to all allergens. Some may have severe allergic rhinitis but no food allergies, for instance, or be extremely sensitive to nuts but not to any other food. Allergies may get worse over time. For example, childhood ragweed allergy may progress to year-round dust and pollen allergy. On the other hand, a person may lose allergic sensitivity. Infant or childhood atopic dermatitis disappears in almost all people, for example. More commonly, what seems to be loss of sensitivity is instead a reduced exposure to allergens or an increased tolerance for the same level of symptoms.

Causes

Mast cells, one of the major players in allergic reactions, capture and display a particular type of antibody, called immunoglobulin type E (IgE) that binds to allergens. Inside mast cells are small chemical-filled packets called granules. Granules contain a variety of potent chemicals, including histamine.

Immunologists separate allergic reactions into two main types: immediate hypersensitivity reactions, which are mainly mast cell-mediated and occur within minutes of contact with allergen, and delayed hypersensitivity reactions, mediated by T cells (a type of white blood cells) and occurring hours to days after exposure.

Inhaled or ingested allergens usually cause immediate hypersensitivity reactions. Allergens bind to IgE antibodies on the surface of mast cells, which spill the contents of their granules out onto neighbouring cells, including blood vessels and nerve cells. Histamine binds to the surfaces of these other cells through special proteins called histamine receptors. Interaction of histamine with receptors on blood vessels causes increased leakiness, leading to the fluid collection, swelling and increased redness. Histamine also stimulates pain receptors, making tissue more sensitive and irritable. Symptoms last from one to several hours following contact.

In the upper airways and eyes, immediate hypersensitivity reactions cause the runny nose and itchy, bloodshot eyes typical of allergic rhinitis. In the gastrointestinal tract, these reactions lead to swelling and irritation of the intestinal lining, which causes the cramping and diarrhoea typical of food allergy. Allergens that enter the circulation may cause hives, angioedema, anaphylaxis, or atopic dermatitis.

Allergens on the skin usually cause delayed hypersensitivity reaction. Roving T cells contact the allergen, setting in motion a more prolonged immune response. This type of allergic response may develop over several days following contact with the allergen, and symptoms may persist for a week or more.

While allergy to specific allergens is not inherited, the likelihood of developing some type of allergy seems to be, at least for many people. If neither parent has allergies, the chances of a child developing allergy is approximately 10-20%; if one parent has allergies, it is 30-50%; and if both have allergies, it is 40-75%.One source of this genetic predisposition is in the ability to produce higher levels of IgE in response to allergens. Those who produce more IgE will develop a stronger allergic sensitivity.

Common allergens…

• The most common airborne allergens are the following: Plant pollens, Animal fur and dander, Body parts from house mites, (microscopic creatures found in all houses) House dust, Mould spores, Cigarette smoke, Solvents, Cleaners
• Common food allergens include the following: Nuts especially peanuts, walnuts and Brazil nuts Fish, mollusks and shellfish, Eggs, Wheat, Milk Food, additives and preservatives
• The following types of drugs commonly cause allergic reactions: Penicillin or other antibiotics, Flu vaccines, Tetanus,
• Common causes of contact dermatitis include the following: Poison ivy, oak, and Nickel or nickel alloys, Latex
• Insects and other arthropods whose bites or stings typically cause allergy include the following: Bees, wasps and hornets, Mosquitoes, Fleas, Scabies

Symptoms

Airborne allergens cause the sneezing, runny nose, and itchy, bloodshot eyes of hay fever ( allergic rhinitis ). They can also affect the lining of the lungs, causing asthma , or the conjunctiva of the eyes, causing conjunctivitis (pink eye).

Allergens in food can cause itching and swelling of the lips and throat, cramps, and diarrhoea . When absorbed into the bloodstream, they may cause hives (urticaria) or more severe reactions involving recurrent, non-inflammatory swelling of the skin, mucous membranes, organs, and brain (angioedema). Some food allergens may cause anaphylaxis , a potentially life-threatening condition marked by tissue swelling, airway constriction, and drop in blood pressure.

In contact with the skin, allergens can cause reddening, itching, and blistering, called contact dermatitis . Skin reactions can also occur from allergens introduced through the airways or gastrointestinal tract. This type of reaction is known as atopic dermatitis .

Symptoms of food allergies depend on the tissues most sensitive to the allergen and whether it is spread systemically by the circulatory system. Gastrointestinal symptoms may include swelling and tingling in the lips, tongue, palate or throat; nausea; cramping; diarrhoea; and gas. Contact dermatitis is marked by reddened, itchy, weepy skin blisters. Allergic rhinitis is characterised by an itchy, runny nose, often with a scratchy or irritated throat due to post-nasal drip. Inflammation of the thin membrane covering the eye (allergic conjunctivitis) causes redness, irritation and increased tearing in the eyes. Asthma causes wheezing , coughing , and shortness of breath .

Prevention

Avoiding allergens is the best means of limiting allergic reactions, this of course can only be achieved once the specific allergen is known. By determining the allergens that are causing reactions, most people can learn to avoid allergic reactions from food, drugs, and contact allergens such as poison ivy or latex. Airborne allergens are more difficult to avoid, although keeping dust and animal dander from collecting in the house may limit exposure. Detox remedies can also be used in many cases to help with the symptoms of the allergen.

Get your allergy testing and food intolerance test done at the Amber Clinic