Allergy – What it means

 

Allergies, simply put, are adverse reactions occurring in a person to otherwise harmless environmental factors.

 

Allergy – The modern day epidemic

 

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”.

 

Allergy – Who is at risk?

 

 

 

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, drug 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.

 

Allergy – The unsuspected offender

 

Allergy can be caused by anything under the sun including the sun. Common allergens include pollen, molds, yeast, fungal spores, dust mites, air borne inhalants, common foods, insect stings and bites and in some cases, certain drugs and cosmetics.

 

Allergy – The role of immunoglobulin E (IgE)

 

IgE antibodies are the prime antibodies concerned with allergic reactions. When a person in 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 measures by serological tests (ELISA, RAST, Etc.).

 

Allergy – The target tissue

 

Since the allergens are extraneous substances the organs/tissues manifesting the allergic 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 pre-dominant symptoms. If the mediators are released in the skin, they produce redness, hives and itching. If this process involves the whole body, it cause a sudden catastrophic allergic reaction known as anaphylaxis.