Our immune system protects us from the outside world. It is a finely tuned network of organs and cells working together effectively and efficiently to remove from our bodies anything that might pose a threat to health. 

Sometimes, however, the system can become overprotective, launching a full-blown attack on one of those harmless substances that previously would have provoked little or no response.  This is an allergy:  an overreaction of the immune system to a harmless substance in our environment. 

'True' allergies

There is frequently some confusion as to what can be strictly classed as an allergy and those conditions that are loosely termed allergies for simplicity.

All true allergies are 'Type I Hypersensitivity reactions', described in detail in later sections.  The term allergy is, however, often used to describe a whole host of clinical conditions, not all of which fit the description.  Some food or drug reactions, for example, are actually delayed-type, or Type IV, hypersensitivity reactions and are not strictly allergies, yet are referred to as such by doctors and patients alike for convenience. 

Definitions

An allergic reaction is an inappropriate immune response to harmless matter in the environment.  Exposure to these substances poses no threat to the body, and so our immune systems are usually able to deal with them without us even noticing.  In some people, though, the system can become hypersensitive to one or more foreign proteins, known as allergens, causing it to overreact whenever that allergen in encountered.  In this way, an allergy is like a phobia of the immune system.

The consequence of this type of overreaction is a cascade of immune substances being overproduced, resulting in excessive amounts of histamine being released in the local area.  It is this that is responsible for the symptoms commonly associated with allergies: the characteristic itchy eyes and runny nose of hay fever, the wheezing and coughing experienced by asthmatics and people allergic to animal dander, and so on.

In severe cases the reaction can spread throughout the entire body, leading to the life-threatening condition known as anaphylactic shock, where the severity of the response in respiratory and cardiovascular tissues can cause inability to breathe and circulatory shock.  Nut allergies are the first thing that springs to mind when talking about anaphylactic shock, but many other types of foods can provoke such a reaction, as can allergies to other incidents such as insect stings.

Adult allergies

Asthma and food allergies are particularly common in older age groups, but any kind can be more problematic in later life simply because there are a greater number of complications and contributing factors.

Increasing age brings with it numerous physiological changes often manifesting in new aches and pains and causing the body to react differently to familiar situations.  Headaches, indigestion, fatigue, mood swings, muscular pain and respiratory irritation can get ignored and dismissed as part of the aging process, but it is important to be aware that they can all be caused by allergies.

The conditions most commonly thought of when we talk about allergies are acute localised reactions, usually treatable with drugs or by avoiding the cause, and are usually fairly short lived and little more than a nuisance.  In some cases, however, an allergy can have a debilitating effect on a persons entire body, effectively taking over their life.

All too often adults are unaware that they are reacting in an adverse way to something in their environment, suffering instead a constant level of ill health that can almost begin to feel normal.

One 47-year-old woman had been suffering ill health for the majority of her life, through conditions such as Irritable Bowel Syndrome, fibromyalgia, headaches, and various recurrent infections.  Her energy levels were reported to be approximately 60% of what they should be.  Yet after intensive investigations by her doctor and a range of specialists it was discovered that the woman was allergic to 18 foods, 17 moulds, five chemicals, and 24 inhalants / pollens! 

Not surprisingly, 2 months after beginning treatment with immunotherapy her general health had improved significantly and her energy levels had increased to 85% of normal.

It is generally agreed that exposure to allergens such as house dust mites and irritants like cigarette smoke have a significant bearing on a person's likelihood of developing allergic diseases.  
      
Genetics also play a large part by determining a person's capacity to produce IgE, one the immune factors involved in an allergic reaction.  A child born to parents who are both allergic has a 75-80% change of being allergic itself.
     
Advances in technology and product manufacture could be partly responsible for the increase in allergic diseases.  It is possible that the more new materials we produce the harder it is for our immune systems to keep up, leading us to a stage where we have molecules in our environment that we are unable to deal with. 

A study published recently in the science journal Nature, for example, revealed that the material used in the non-stick cooking product Teflon could produce toxic chemicals when exposed to intense heat, causing widespread worry for the safety of consumers. 

The increase in apparent chemical sensitivity in the workplace as a major cause of occupational illness also indicates that we are bombarding our systems with more than they can handle, faster than they are able to learn how to deal with it.

Written by Claire Jackson. 

03/06/2009