The term allergy is used to describe a response, within the body, to a substance, which is not necessarily harmful in itself, but results in an immune response and a reaction that causes symptoms and disease in a predisposed person, which in turn can cause inconvenience, or a great deal of misery..
An allergy is everything from a runny nose, itchy eyes and palate to skin rash. It aggravates the sense of smell, sight, tastes and touch causing irritation, extreme disability and sometimes fatality. It occurs when the body’s immune system overreacts to normally harmless substances..
Allergy is widespread and affects approximately one in four of the population in the UK at some time in their lives. Each year the numbers are increasing by 5% with as many as half of all those affected being children..
What causes an Allergy ?
Allergic reactions are caused by substances in the environment known as allergens. Almost anything can be an allergen for someone. Allergens contain protein, which is often regarded as a constituent of the food we we eat. In fact it is an organic compound, containing hydrogen, oxygen and nitrogen, which form an important part of living organisms..
Allergy
The most common allergens are:
pollen from trees and grasses, house dust mite, moulds, pets such as cats and dogs, insects like wasps and bees, industrial and household chemicals, medicines, and foods such as milk and eggs. .
Less common allergens include nuts, fruit and latex..
There are some non-protein allergens which include drugs such as penicillin. For these to cause an allergic response they need to be bound to a protein once they are in the body..
An allergic person’s immune system believes allergens to be damaging and so produces a special type of antibody (IgE) to attack the invading material. This leads other blood cells to release further chemicals (including histamine) which together cause the symptoms of an allergic reaction..
The most common symptoms are:
sneezing , runny nose, itchy eyes and ears, severe wheezing, coughing, shortness of breath, sinus problems, a sore palate and nettle-like rash..
It should be understood that all the symptoms mentioned can be caused by factors other than allergy. Indeed some of the conditions are diseases in themselves..
When asthma, eczema, headaches, lethargy, loss of concentration and sensitivity to everyday foods such as cheese, fish and fruit are taken into account the full scale of allergy can be appreciated..
What is allergy?
Allergy can be described as a malfunction of the human immune system causing a violent reaction against normally harmless substances in our natural environment. In this context, such substances are generally referred to as “allergens”. The reaction creates an inflammation which, in turn, can lead to a variety of symptoms such as hay fever, eczema, asthma and other conditions popularly referred to as allergies.
There are genetic and environmental risk factors. To develop allergic symptoms, one must first be exposed to the specific allergen for some time to build up the allergic sensitivity, and then once more to trigger the allergic reaction. Environmental factors, such as smoking and pollution, will also add to the risk.
Initially, allergy often appears as seemingly benign condition, such as hay fever during the pollen season. In fact, many people gradually build up an allergic condition over many years before experiencing any symptoms whatsoever.
However, for some unfortunate people, a certain food or drug or an ordinary insect bite can result in sudden, life-threatening anaphylactic shock. Furthermore, of those allergies which start as eczema or gastrointestinal problems, many evolve into asthma, frequently involving respiratory symptoms such as hyperreactivity and obstruction of the airways. This direct path of development, widely referred to as “the allergy march” (1) is of prime interest for the research and development carried out within Phadia.
Our basic understanding of allergy has evolved from the discovery in 1967 of a previously unknown antibody, Immunoglobulin E or “IgE”, by scientists in Uppsala and Baltimore. The most significant property of IgE antibodies is that they can be specific for hundreds of different allergens. Continued research has significantly advanced our knowledge regarding, for example, the interaction between IgE and inflammatory cells.
For effective asthma medication, one needs to look beyond the obvious symptoms. Anti-histamines, for example, may provide temporary relief by masking the symptoms, but have virtually no effect on the underlying inflammation. Other pharmaceuticals, known to be effective for seasonal allergies, must be administered weeks before exposure. The clinical use of inhaled steroids is currently gaining ground due to their anti-inflammatory effects, although overtreatment may have serious side-effects. To ensure the lowest effective dosage throughout treatment, the laboratory can periodically monitor the occurence in serum of ECP (2) released from inflammatory cells. Eosinophilic Cationic Protein is a protein generated in certain white blood cells actively engaged in the immune defense system. Using a diagnostic test developed by Phadia, ECP can be detected in body fluids.
References
1.Saarinen U M, et al. Lancet 1995;346:1065-1069
2.De Backer. Am J Respir 1996;153:A336
What is allergy?
Allergy is an overreaction of the immune system to substances that are otherwise harmless. The most common allergies are caused by everyday, airborne particles such as pollens or house dust mites. For many people, these tiny particles are insignificant. But for people with allergy, they can trigger seasonal or chronic respiratory conditions, such as hay fever or asthma.
Allergy significantly reduces people’s quality of life. It affects not only their personal, but also their professional lives. Coping with itching eyes and a blocked nose has its costs for the individual, but also for society in terms of poorer quality of life, lower productivity levels at work and increased sick leave – not to mention the cost of healthcare and medication.
What is allergy?
IMPORTANT The information provided is of a general nature and should not be used as a substitute for professional advice. If you think you may suffer from an allergic or other disease that requires attention, you should discuss it with your family doctor. The content of the information articles and all illustrations on this website remains the intellectual property of Dr Raymond Mullins and cannot be reproduced without written permission.
What causes allergy symptoms?
Underneath the lining of the skin, gut, lungs, nose and eyes are mast cells. These are designed to kill worms and parasites. Mast cells are like “land-mines”, and contain “bags” filled with irritant chemicals including histamine. When these are released in small amounts, they cause irritation. In larger amounts, they can cause rashes, the sneezing of hay fever and the wheeze of asthma.
What happens during an allergic reaction?
Mast cells are armed with proteins called IgE antibodies, which act as remote sensors in the local environment. A person allergic to peanut, for example, will have IgE antibodies capable of recognising the shape of peanut protein (the allergen), in much the same way that a lock “recognises” the shape of a key. When this happens, mast cells dump their contents into the tissues, causing an allergic reaction. Depending on where the reaction occurs, it may result in itchy skin rashes, itchy watery eyes, sneezing and runny nose, cough and wheeze or even more serious symptoms known as anaphylaxis.
Common allergy triggers
We can have allergic reactions to what we swallow (food or medicines), what we breathe in / inhale (eg. dust mite, pollens, mold spores or animal allergen), what we touch (eg. plants, animals, perfumes, cosmetic preservatives) or what is injected (eg. insect stings, medications, blood transfusions).
Allergies tend to run in families
Allergic people have a greater than average tendency to produce IgE antibodies to common environmental substances. This tendency is inherited and occurs in around 2 in 5 people. If you have one allergic parent, for example, there is around a 1 in 3 chance of developing allergies yourself. If you have two allergic parents, the risk doubles. In other words, you can pick your friends but not your parents!
Allergy is increasing
Allergy is more common now than in our parents’ and grandparents’ generation. A number of careful studies in Australia and abroad have shown that the frequency of hay fever, asthma, eczema and even food allergy appears to have doubled in the last 30 years. It is a true increase, and not just because doctors are better at diagnosing allergies. In the last 10 years, similar increases in food allergy have also been observed in Australia, the UK and USA, particularly in peanut allergy. The explanation for this increase also remains unexplained.
Why is allergy increasing?
There are many theories to explain the fact that the incidence of allergy has approximately doubled in the last 20-30 years in almost every country in which it has been studied. Theories include:
-Less exposure to parasitic disease in the developed world. This leaves one arm of the immune system with nothing to do except react against harmless “allergens”.
Lower rates of breast-feeding.
-Exposure to air pollution, particularly exposure to particulate matter from diesel fumes.
-Exposure to cigarette smoke.
-The “hygiene hypothesis”, whereby exposure to less infection early in life increases the risk of developing allergies.
-Low vitamin D levels, and many others
Unfortunately, there is no conclusive evidence at this time to easily explain the dramatic rise observed in recent generations
The Hygiene Hypothesis
Babies are born with an immune system which is inherently biased towards developing allergic-like reactions. These are called “type 2 response”. A more balanced immune response is thought to require early exposure to infections. The first year of life appears to be the critical time in which this balance changes to a form of immunity that makes allergy less likely. Early exposure to infection is thought to “reset the balance” of the immune system by stimulating so-called “type 1 immune responses” instead. Recent studies have shown that multiple upper respiratory tract infections (“colds and flu’s”) in the first year of life may reduce the risk of developing asthma and hay fever by up to 50 %. There is also evidence that exposure to some gut bacteria may also play a role in modifying how the immune system develops in the first year of life, leading to trials of so-called “probiotics” in an attempt to reduce the risk.
There is no convincing evidence that…
… food additives, preservatives, pesticides or vaccination contributes to a higher risk of allergy.
References
Ball TM et al. Siblings, day-care attendance, and the risk of asthma and wheezing during childhood. New Eng J Med 2000; 343: 538-43.
Sporik R et al. Exposure to house dust mite and the development of asthma in childhood. New England Journal of Medicine 1990; 323: 502-7.
Von Mutius E. The environmental predictors of allergic disease. J Allergy Clin Immunol 2000; 105: 9-19.
Matricardi PM et al. Exposure to foodborne and orofecal microbes versus airborne viruses in relation to atopy and allergic asthma: epidemiological study. BMJ 2000; 320: 412-7.
Wickens K et al. Antibiotic use in early childhood and the development of asthma. Clin Exp Allergy 1999; 29: 766-71.
Kramer U et al. Age of entry to day nursery and allergy in later childhood. The Lancet 1999; 353: 450-4.
Strannegard O et al. The cause of the increasing prevalence of allergy: is atopy a microbial deprivation disorder? Allergy 2001; 56: 91-102.
Mallol J et al. ISAAC findings in children aged 13-14 years an overview. ACI International 1999; 11: 176-82.
Holgate ST. Allergic disorders. BMJ 2000; 320: 231-4.
Salvi S. Pollution and allergic airways disease. Current Opinion in Allergy and Clinical Immunology 2001; 1: 35-42.