What Are Allergies and Why Do We Have Allergic Reactions?

An allergy is an inappropriate and potentially damaging immune system response to a substance in the environment, such as pollen or house dust mites.

If a person reacts to such a substance, it means their body has become hypersensitive to that substance. Another person in the same place at the same time might not react. A substance that causes an allergic reaction is called an allergen.

The Immune System

The immune system is made up of many different protective elements, such as the skin, stomach acid, and the cilia (hair-like structures) that line part of the respiratory tract. These all work to keep out harmful bacteria, destroy them or expel them when they enter the body.

There are other parts of the system too. An enzyme called lysozyme (found in many of the body’s fluids) can break down the walls of many bacteria. Also part of this system are the so-called “good bacteria”, such as those that normally inhabit the digestive system.

The immune system has two parts:

• The Innate Immune System is the body's knee-jerk defence against bacteria and other foreign particles, but it can't learn or improve with repeated exposures.
• The Adaptive Immune System kicks into gear if the innate system fails to deal with the intruder. It produces tailor-made "antibodies" to attack that specific intruder. It learns from this encounter, remembers the intruder, and swiftly deals with a repeat offense, preventing us from getting certain diseases more than once in our lives.

Inflammation

The inflammation that is a characteristic part of an allergic reaction is not a bad thing, even though it is uncomfortable. It is the immune system's way of attacking the intruder. Inflammation increases blood supply so more of the immune system's cells in the blood are available and this helps white cells move out of blood vessels to where they are needed.

The Allergic Response

Responses to allergens have two phases:

• Early Phase Reactions occur within the first hour of exposure and include sneezing, dripping nose, and itchy nose and eyes.
• Late Phase Reactions take longer and can last up to 24 hours after exposure. Symptoms include nasal congestion, puffy and watery eyes, sleep disturbances, tiredness, and irritability, and a blocked up groggy feeling.

The link below takes you to the introductory page of an excellent website devoted to exploring and explaining allergies.