Allergies, simply put, are adverse reactions occurring in a person to otherwise harmless environmental factors.
In India 20-30% of the population, about 250-300 million suffer from various allergic diseases. People in metropolitan cities are more prone to develop allergies, with Bangalore being termed the "Allergy Capital of India".
Whether or not a person develops an allergy is determined by his genetic makeup,exposure to potential allergens in early life and environmental triggers.
Every individual has an inherent defense mechanism to mount a protective response against foreign substances (toxins, microbes, proteins, antigens, drugs etc.). The ability to mount such a response is genetically determined and is mediated by specific antibodies. Hence most of the allergic individuals have a positive family history.
When a genetically predisposed individual is exposed to a potential allergen (protein/polypeptide antigen), his immune system becomes sensitized for that particular allergen. Future exposure to the same allergen triggers the release of chemical mediators (histamine,bradykinin) resulting in allergic manifestations.
Allergies have a genetic component. Children are more likely to develop allergies if their parents have allergies
If you have an allergy, your immune system overreacts to a substance you inhaled, touched or ate.
Your immune system controls how your body defends itself. For instance, if you have an allergy to pollen, your immune system identifies pollen as an invader or allergen. Your immune system overreacts by producing antibodies called Immunoglobulin E (IgE). These antibodies travel to cells that release chemicals, causing an allergic reaction. These reactions can range from annoying sneezing and sniffling to a life-threatening response called anaphylaxis.
So how can you be sure which allergens are responsible for your symptoms? Allergy tests, combined with a physical examination and medical history, can give precise information about what you are, as well as what you are not, allergic to. For instance, perhaps you or a family member has allergy symptoms and your household includes a pet. You don't have to avoid contact with the pet if allergy testing shows an allergy to dust mites but not to pet dander.
Many people with untreated allergy symptoms aren't aware of how much better they will feel once their symptoms are properly diagnosed and managed.
Symptoms which usually prompt an allergist to perform testing include:
• Respiratory: itchy eyes, nose or throat; nasal congestion, runny nose, watery eyes, chest congestion, cough or wheezing
• Skin: itchiness or eczema
• Abdominal: vomiting or cramping and diarrhea consistently after eating certain foods
• Severe reactions to stinging insect stings (other than swelling at the site of the sting)
• Anaphylaxis (pronounced an-a-fi-LAK-sis): a serious allergic reaction that affects many parts of the body at the same time
Allergy can be caused by anything under the sun including the sun. Common allergens include pollen, molds, yeasts, fungal spores, dust mites, air borne inhalants, common foods, insect stings and bites and in some cases, certain drugs and cosmetics.
IgE antibodies are the prime antibodies concerned with allergic reactions. When a person is first exposed to an allergen, IgE antibodies are produced against the offending allergen. These IgE antibodies bind to the surface of mast cells and trigger the release of chemical mediators such as Histamine and Bradykinin. The body can produce a specific variation of IgE antibody for each perceived allergen it encounters. These specific IgE antibodies present in the human serum can be measured by serological tests (ELISA, RAST, etc.).
Since the allergens are extraneous substances the organs/ tissues manifesting theallergic reactions are those that are exposed to the environment like the nose, throat, lungs, skin and gastro intestinal tract (GIT). The mast cells are present abundantly in these areas.
If the mast cells of the respiratory tract are triggered, the chemical mediators released will cause a running nose, sneezing, ear discharge, itchy tongue and difficulty in breathing or swallowing. If the mediators are released in the GIT, abdominal cramps, diarrhea and vomiting are the predominant symptoms. If the mediators are released in the skin, they produce redness, hives, and itching. If this process involves the whole body, it causes a sudden catastrophic allergic reaction known as anaphylaxis.