What is allergy? Definition

Allergy is defined as an abnormal response of the body’s defense mechanism to an external substance – a substance that the body foresees as an enemy or a damaging force.

This substance may have entered the body through inhalation or ingestion or injection or it may just have had skin contact. Another way to diagnose the allergen is to undergo certain diagnostic tests.

Allergy can be terrible. You get those pink-colored raised itching rashes on your skin, a running or blocked nose, watery eyes, swollen lips, and even shortness of breath.

Allergy is basically an abnormal hypersensitive reaction or a disorder of your body to a substance or substances (allergens).  It is repulsion or an aversion, that the body shows to these allergens by directing its defensive network against them.

It is as though your body hates that substance (allergen) and therefore loathes it and shows it by producing an allergy reaction.

Allergies are one of the most common chronic conditions worldwide. The reason for allergy being chronic is that a person gets repeatedly exposed to the allergen.

Being chronic makes this health condition even more damning. In addition, it is not possible to forecast or predict if and when you are going to be a victim of which allergen.

An allergic reaction can take a few seconds, a few minutes, or a few hours, or rarely as long as a day to develop. It depends on the type of substance that has caused the allergy and how sensitive your body is to it.

Many allergic reactions are mild while some may be severe. Some reactions may be confined to a part of the body while some may affect the entire body.

In addition, these allergy problems can last for one to two days and can even recur.  To make it worse, many times, the root cause of the allergy in the body cannot be identified.

For the same reason, why some people develop allergies and others do not, cannot be explained. However, it is seen that allergic reactions commonly affect those who have a family history.

Such people are more susceptible and vulnerable to its attacks than those without a family history.

Allergy is defined as an abnormal response of the body’s defense mechanism to an external substance – a substance that the body foresees as an enemy or a damaging force.

This substance may have entered the body through inhalation or ingestion or injection or it may just have had skin contact.

How and why do you get allergy? Its causes

Our body has a defense mechanism, which fights off any unwanted substances that come in contact with it. Those substances could be viruses, bacteria, or parasitic worms, which enter the body through anything that you have eaten or breathed in, or through a wound in the skin.

The immune or the defense system of our body consists of a network of cells, tissues, and organs that work together and protect the body from any harm that these invading organisms can cause.

The white blood cells (WBCs), also called leucocytes or leukocytes, are among the more active and important cells of the immune system. The mast cells are a type of white blood cell, which play a fundamental role in the regulation of the immune system of the body.

The invading substance is called the antigen and the immune cells  (immunoglobins E) are called the antibodies. The defense interaction that occurs between the antigen and the antibodies is called the antigen-antibody reaction.

This reaction triggers the release of certain chemicals, of which histamine is the main component.

This antigen-antibody reaction manifests itself in various ways by producing signs and symptoms of allergy. Note that not all people develop manifestations of this reaction.

In an allergy, the immune system overreacts to the allergen by directing the immune cells against it. This results in an antigen-antibody reaction, which manifests in allergy symptoms.

The first time you are exposed to an allergen, you may not develop any reaction. But, the immune system starts to produce antibodies against that allergen.

The next exposure to that same allergen will evoke an allergic reaction because the antibodies are now present in your blood to cause an antigen-antibody reaction.

Allergic reactions or allergy symptoms may manifest as simple skin rash or can come as an anaphylactic shock due to injection of drugs like Penicillin. An anaphylactic shock can be life-threatening and is to be treated on an emergency basis.

How do you know if you are allergic to something?

It is said that anything under the sun can cause allergies, including the sun itself. Therefore, sometimes it can be difficult to know the reason, which has caused the allergic reaction.

However, the allergic victim from his pre-allergic circumstances, himself may be in a position to determine what has caused his allergy. He should try to identify anything; he has come in contact with or eaten out of routine, which could be the reason for his allergic reaction.

Trigger factors that can cause allergy

There are, however, certain common known allergens, that can be the reason behind your allergy. They are:

  • Skin contact with pollen dust, animal hair, dander, fur, and certain weeds on a farm
  • Other common allergens, which can cause skin allergies are metals, plants, cosmetics, latex, medications, and perfumes.
    • Among the metals, the most common ones that can give rise to allergy are gold and nickel found in jewelry products,  cobalt chloride found in hair dyes and antiperspirants
    • A mercury compound called Thimerosal used as a preservative in vaccines
    • Formaldehyde used as a preservative in various products
    • Neomycin sulfate used in topical antibiotic powders, creams, and ointments
  • Cigarette smoke and diesel fumes can also cause eye allergy
  • Inhalation of certain incense aromas or smoke, or pollen released by weeds into the air
  • Certain people react to cold climates while some to hot climates
  • Stings from insects, especially bees
  • Extreme emotion
  • Ingestion of drugs like antibiotics and aspirin
  • Eating certain foods, especially seafood like shellfish, crabs, lobster, peanuts, eggs, etc.
  • Anaphylaxis is a severe form of allergy, which is caused by the injection of the drug, penicillin. It can be fatal.

Common areas of the body affected by allergy

  • The eyes, nose, sinuses, and throat. These parts of the body are affected due to breathing in allergens. The nasal lining becomes swollen and produces excessive mucus. You may get a watery or a blocked nose and you may even have excessive sneezing. Your eyes may water and you may get a sore throat.
  • The chest and the lungs. The lungs are affected due to breathing in an allergen or allergens. The lining of the airway tubes gets swollen and secretes mucus. This can cause blockage of the airway passage and make breathing difficult. Asthma is the presenting symptom.
  • The stomach and intestines. Common allergens, which cause stomach allergies include peanuts, seafood, dairy products, and eggs. Symptoms include an upset stomach.
  •  The skin. Skin allergy occurs due to direct contact of the skin with the allergen. This skin allergy may manifest as urticaria (hives) or eczema. Hives present as white itchy bumps and eczema as dry, red, itchy skin.