How Allergies Work

Allergy is a very complex phenomenon involving many different factors. With heart disease, the new scanning techniques allow cardiologists to make fairly accurate diagnoses in a way which wasn’t possible twenty years ago, but that is not at all the case for allergy specialists.

In the last twenty years, there has been a significant amount of scientific progress made in relation to our understanding of what happens within cells when you have an allergic response. The more that is understood about the chain of event that is triggered by a piece of pollen or a house-dust mite, the more we can begin to unravel the tangled relationship between the genetic and the environmental factors that are involved.

The term of allergy derives from the Greek words allos, meaning other, and ergon meaning work. The term itself is quite broad and can cover any kind of reaction involving the immune system, however, for most sufferers; it involves a sensitivity to a particular chemical or substance. This is known as Type 1 hypersensitivity.

It is the job of our immune system to protect us from foreign invaders, known as antigens. From the moment a baby emerges from the womb, he or she is exposed to all kinds of bacteria and viruses that would prove fatal were the body not equipped with an awesomely sophisticated way of repelling them. The cold viruses that swirl around and infect us every winter, for example, are mostly harmless because the body can recognise the invader and mount a defence.

When a germ is breathed in, or enters the bloodstream, our immune system produces antibodies – molecules designed to latch on to particular viruses or bacteria and disable them before they can do harm. This is fine when the body needs to protect itself from an antigen such as pneumococcal bacteria. However, in the case of allergies, antibodies are marshalled against the wrong enemy. They go into battle against substances that are very common and which may be all around us, such as grass pollen.

A chemical or substance that produces an allergic response is known as an allergen. As we will see, this could be the coating on a piece of pollen, mould from a fir tree, or the saliva of a cat. An allergen is not a particular substance in itself, but really a description of the way people react to it. A feather-filled pillow can mean luxurious sleep to some of us, for others, it equates to a night of misery, wheezing and a constantly runny nose.

The first stage of an allergic response is known as sensitisation – the first time when an antibody known as immunoglobulin E or IgE is produced in response to a common and usually harmless substance. IgE is a protein molecule which is common in most allergic reactions and its level can be measured through a blood test. Immunoglobulin evolved in humans as a way of fighting off parasites, such as ringworm, and levels of it are still high in those living in tropical countries where there are parasitic illnesses.

The most important stage in an allergic reaction is known as degranulation. This is where the mast cells start to break up and release some of their granules, which contain chemicals known as inflammatory mediators which end up in surrounding tissues. It is this process that appears to cause so many of the problems associated with an allergic response. A cascade effect is produced, with chemical after chemical being released as part of the defence system. One of those released is histamine, which plays such an important role in hay fever. The mast cells also release what is known as messenger chemicals and, in particular, some which are called leukotrienes. These are damaging, and go on to cause further inflammation in different tissues.

This whole chain of chemical events results in several unwanted effects such as the widening of blood vessels in the nose, the stimulation of nerves, bronchoconstriction in the lungs (where the airways start to narrow) and contraction of smooth muscle in the gut. The symptoms that are experienced in allergies – the runny nose, itchiness, stomach problems or the breathlessness – all come from this complex immune reaction.

Related Posts:
%RELATEDPOSTS%