Kokova Magazine

Allergy and intolerance seem to be on the rise - with more people finding they have sensitivity to certain foods or substances that they encounter on a day-to-day basis.

With Food Allergy and Intolerance Week running from the 23rd to the 29th January we ask 'what is an allergy?' and 'how does it differ to an intolerance or sensitivity?'

What is Allergy?

The term allergy is used to describe a particular response by the body's immune system to a substance in the environment (including foods), 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.

This response occurs in predisposed individuals and results in the development of a particular antibody (IgE) against the substance.

The next time the person meets this substance the antibody reaction causes the release of certain chemicals into the body. These chemicals cause the symptoms of allergic disease.

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.

Examples of allergic disorders include asthma, eczema, hayfever and year-round nasal symptoms, urticaria (hives or nettlerash) and anaphylaxis.

The tendency to develop allergic disease in this way is inherited. This allergic tendency is called atopy.

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.

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 an Allergen?

Substances which provoke production of IgE and cause allergy in a susceptible person are known as allergens.

Almost anything can be an allergen but some substances are much more common allergens than others, for example house dust mites, pollen from trees and grasses, cats, dogs, insects such as wasps and bees, milk, eggs and peanuts.

Less common allergens include tree nuts, fruit, and latex.

Most allergens are proteins but there are some non-protein allergens such as penicillin and some other drugs. For these to cause an allergic response, they need to be bound to a protein once they are in the body.

What is the difference between Allergy, Intolerance, and Sensitivity?

Although the word Allergy is commonly used to describe any unpleasant reaction to a drug, food, insect sting, or chemical, this can be misleading. The word should only really be used to describe a reaction produced by the immune system when the body meets a normally harmless substance, which has been "remembered" from a previous exposure and subsequently produces the IgE antibody.

Sensitivity is an exaggeration of a normal side effect produced by contact with a substance. For example, the amount of caffeine in a single cup of coffee may cause palpitations and trembling in a sensitive person, where this would normally only occur after far higher doses of caffeine.

Intolerance happens for a variety of reasons including the production of different types of antibody against the substance (not the IgE antibody produced in allergy), or because your body does not produce sufficient quantities of a particular enzyme/chemical, which is needed to break down a food and aid digestion.

How do you know if you have an allergy?

The most useful tool in deciding whether someone is allergic is to take an 'allergy history'. A good allergy clinician can usually identify the likely allergens from the history alone, and allergy tests are often not needed.

However there are occasions when tests can be useful to confirm the diagnosis. This is especially important if you have had a severe reaction and if there is any confusion as to whether your symptoms are caused by a true allergy (involving the production of IgE) or whether some other process is involved.

There is no point in having an allergy test if either the sufferer or the doctor is not prepared to act on the results.

What Allergy Tests are available?

The type of test to be carried out will depend upon your symptoms, the condition of your skin, and any medication you are taking.

Skin Prick Testing
This test measures specific IgE attached to cells in the skin. This is probably the most commonly used allergy test and is appropriate for inhaled and ingested (eaten) allergies.

• It is usually carried out on the inner forearm
• If the patient has bad eczema on the area under the test then the test can be performed on the back
• The test allergens are selected in accordance with the patient's history
• As few as 3 or 4 or up to about 25 allergens can be tested
• The name of each thing to be tested is written on the arm (or a number may be used)
• A drop of the allergen (extract) solution is placed by the relevant name or number
• The skin is then pricked through the drop using the tip of a lancet - this can feel a little uncomfortable but should not be painful
• The patient needs to avoid taking antihistamines and certain other medications for several days before the test

If the test is positive, the skin becomes itchy within a few minutes and then becomes red and swollen with a "weal" in the centre (very much like the reaction to a nettle sting).

The weal has a raised edge which slowly expands to reach its maximum size in about 15 minutes, clearing for most people within an hour. The size of the weal varies with the average being 3-5 mm in diameter.

It should be noted the size of the weal does not indicate the severity of symptoms. The test tells us that a level of antibodies is present which may be causing your symptoms.

Also included is a negative and positive control. The negative control is a saline (salt-water) solution, to which a response is not expected. If a patient reacts to a negative control, this indicates that the skin is extremely sensitive and that the results from the test need to be interpreted with care.

The positive control solution contains histamine, to which everyone is expected to react. Failure to do so means that something (e.g. medicines taken by the patient) is blocking the response to the allergens, and the test is invalid.

The skin prick test introduces such a tiny amount of allergen into the skin that testing is very safe and almost any age group can be tested. The most common side effect is itching at the site of the test.

Where there is a history of a severe allergic reaction, skin testing may not be appropriate.

These tests can be carried out on all age groups including babies, although the response will be considerably smaller than in an adult. Skin prick testing is usually the first test recommended when an allergy is suspected.

It is a simple, quick and inexpensive form of testing. It can give useful information in all forms of allergy and provides results within 15-20 minutes. Skin tests should be carried out by specially trained nurses or doctors who can treat any side-effects that might arise.

Blood Tests

Blood tests measure the amount of IgE circulating in the blood. The test is carried out on a small sample of blood, usually taken from a vein in the arm in the usual way. The sample is then sent to a laboratory and the results are available in 7 to 14 days.

These tests are particularly useful when the patient has a risk of severe allergic reaction, when extensive eczema makes skin prick testing impractical, when antihistamine medication cannot be stopped because of severe symptoms, or when unusual and rare allergens are suspected.

IgE results are reported either as 'Classes' ranging from 0 (negative) to 6 (extremely high), or as actual levels. Interpreting the results requires care and experience and should always be done by a trained clinician in conjunction with the clinical history.

Some IgE blood-testing kits have now become available for the patient to use at home. IgE test results are not easy to interpret; very occasionally false positive and false negative results are possible, and the presence of IgE in a test does not necessarily mean that the substance is actually causing the patient's symptoms. For these reasons, home testing of IgE is not recommended without reference to either a healthcare professional or suitable support information.

Patch Testing

This test is performed in cases of contact dermatitis (Eczema) where allergy is suspected.

The allergens are prepared in appropriate concentrations in white soft paraffin (e.g. Vaseline) and are then spread on to discs, 1cm in diameter. The discs (which are usually made of special metal which cannot themselves provoke a reaction) are placed on the skin, usually on the back, and are kept in place by hypoallergenic tape.

The skin is marked appropriately and the patient is asked to keep the skin dry. The patches are left in place for 48 hours. After this time the discs are removed, the skin is examined and any redness or swelling is noted. The skin is re-examined after a further 48 hours for any remaining local redness or swelling.

The interpretation of this form of testing is not as simple as it sounds and tends to be carried out by dermatology departments in hospitals. The symptoms of contact dermatitis need to be brought under control before patch testing can be carried out, or the results will be unreliable. Steroid creams need to be stopped for 3-4 weeks before testing as they may suppress the test response.

Can we test for Food Intolerance?

IgG blood tests have become available which have shown some promising results in identifying the foods that may be responsible for causing symptoms in some cases of migraine, arthritis and irritable bowel syndrome. However food intolerance can occur in various ways and this test will not identify all types of food intolerance. IgG tests are not tests for true food allergy.

The 'gold standard' test for food intolerance remains the elimination and challenge diet (see Food Intolerance fact sheet).

Are there other forms of Testing?

Other (Non-conventional) Allergy Tests are not considered to be relevant, standardised or repeatable and are considered to have no place in the diagnosis of allergy. These include Applied Kinesiology (measures muscle strength), Auricular Cardiac Reflex Method (measures strongest pulse at wrist), Hair Analysis, Leukocytotoxic Tests and Vega Testing ( measures the electromagnetic fields produced by the sufferer).

If in doubt, always request evidence of the results of approved clinical trials.

Courtesy of www.allergyuk.org

Anaphylaxis - Key information

Food allergy occurs when the body’s immune system reacts to an ingredient that is harmless to most people. The food that causes the response is known as an allergen.

Anaphylaxis is a severe allergic reaction - the extreme end of the allergic spectrum. Symptoms may include generalised flushing, difficulty in breathing and can result in cardiac arrest and death.

Common causes of anaphylaxis include foods such as peanuts, tree nuts, sesame, fish, shellfish, dairy products and eggs. Non-food causes include wasp or bee stings, natural latex (rubber), penicillin or any other drug or injection.

Acute, severe food allergy is thought to affect half a million people.

The prevalence of food allergy is at its highest in young children (about one in 17 children). In most cases the allergy is mild. Around 80-90 per cent of children outgrow their sensitivity by the age of five. Children are very likely to outgrow an allergy to milk, eggs, soy or wheat. Allergies to peanuts, tree nuts, shellfish or fish are less frequently outgrown.

Research suggests that around one in 70 children across the UK are allergic to peanuts. A House of Commons report in 2004 suggests that the figure may now be as high as one in 50 – a quarter of a million children.

Anaphylaxis is treated with adrenaline (which is also called epinephrine). Pre-loaded adrenaline injection kits – EpiPen or Anapen – are available on prescription for those thought to be at risk of a severe reaction.

Allergic disorders affect all ages, both sexes and all social and ethnic groups in the UK.

International comparisons show that the UK population has the highest prevalence of allergy in Europe and ranks among the highest in the world.

Disease frequencies of the more serious and systemic allergies, e.g. anaphylaxis, drug and food allergy, are increasing fast

The rise of allergic diseases over the last three decades cannot be reliably explained although a number of theories have been considered to do with changes in our environment as a consequence of increasing affluence and modern lifestyles

Numbers of deaths due to allergy are difficult to assess. There is evidence that anaphylaxis causes some 10 to 20 deaths per year but many of these are not recorded as such on the death certificate.

Courtesy of www.anaphylaxis.org.uk