A lot of people suffer from allergies without realising so. Wise up and find out if you or your child suffers from allergies with our simple guide.

What exactly is an Allergy?

Allergy is a disorder of the immune system that is often called atopy. Allergic reactions occur to environmental substances known as allergens; these reactions are acquired, predictable and rapid. Strictly, allergy is one of four forms of hypersensitivity and is called type I (or immediate) hypersensitivity. It is characterised by excessive activation of certain white blood cells called mast cells and basophiles by a type of antibody, known as IgE, resulting in an extreme inflammatory response.

Basically, an allergy is an abnormal reaction by a person's immune system against a normally harmless substance. A person without allergies would have no reaction to this substance, but when a person who is allergic encounters the trigger, the body reacts by releasing chemicals, which cause allergy symptoms. However, just because there is a cause and effect between exposure to a substance and the development of symptoms, it does not always mean that a person is allergic to that substance. For example, medications have known and expected side effects; a person experiencing one of these side effects is not necessarily allergic to that medication.

Itch Much?

Common allergic reactions include eczema, hives, hay fever, asthma, food allergies, and reactions to the venom of stinging insects such as wasps and bees. Mild allergies like hay fever are highly prevalent in the human population and cause symptoms such as allergic conjunctivitis, itchiness and runny nose. Similarly, conditions such as asthma are common, in which allergy plays a major role. In some people, severe allergies to environmental or dietary allergens, or to medication, occur that may result in life threatening anaphylactic reactions and potentially death.

Classification and History

The concept 'allergy' was originally introduced in 1906 by the Viennese pediatrician Clemens von Pirquet, after noting that some of his patients were hypersensitive to normally innocuous entities such as dust, pollen, or certain foods. Pirquet called this phenomenon 'allergy' from the Greek words alios meaning 'other' and ergon meaning 'work'. Historically, all forms of hypersensitivity were classified as allergies, and all were thought to be caused by an improper activation of the immune system.

In 1963, a new classification scheme was designed by Philip Gell and Robin Coombs that described four types of hypersensitivity reactions, known as Type I to Type IV hypersensitivity. With this new classification, the word 'allergy' was restricted to only type I hypersensitivities (also called immediate hypersensitivity), which are characterised as rapidly developing reactions.

Are you Suffering from an Allergy?

The symptoms of allergies vary depending upon the type of allergic disease, as well as the age of the person with the allergy. In some cases, a person may be experiencing symptoms of allergies without being aware that they have an allergic disease. Learn more about the symptoms of various allergic diseases, as well as what to look for if you suspect that you or your child may have allergies.

Allergy testing involves having a skin or blood test to find out what substance, or allergen, may trigger an allergic response in a person. Skin tests are usually done because they are rapid, reliable, and generally less expensive than blood tests, but either type of test may be used.

"Common allergic reactions include eczema, hives, hay fiver, asthma, food allergies, and reactions to the venom or stinging insects such as wasps and bees."

Skin Test

Skin testing remains the test of choice for the diagnosis of most allergies. In the past, this testing was often referred to as 'scratch testing', which is a good description of how the test is performed.

Most allergists refer to skin testing as 'prick testing', which is similar, but less traumatic, than scratch testing. Other tests, such as intradermal skin testing, may also be used for certain people or in certain situations.

Blood Test

Allergy blood tests look for substances in the blood called antibodies. Blood tests are not as sensitive as skin tests but are often used for people who are not able to have skin tests. The most common type of blood test used is the enzyme-linked immunosorbent assay (ELISA, EIA). It measures the blood level of a type of antibody (called immunoglobulin E, or IgE) that the body may make in response to certain allergens. IgE levels are often higher in people who have allergies or asthma.

Types of Allergies

• Skin Allergy

The skin forms an effective barrier to the entry of most allergens, but can be breached by local injection of small amounts of allergen, for example by a stinging insect. The entry of allergen causes a localised allergic reaction. Histamine released by mast cells activated by allergen in the skin causes large, itchy red swellings beneath the skin. A more prolonged inflammatory response is sometimes seen in the skin most often in atopic children. They develop a persistent skin rash called eczema, due to a chronic inflammatory response similar to that seen in the bronchial walls of patients with asthma.

• Allergic Rhinitis

Allergic rhinitis is characterised by local edema leading to nasal obstruction, a nasal discharge and irritation of the nose. A similar reaction to airborne allergens deposited on the conjunctiva of the eye is called allergic conjunctivitis. Allergic rhinitis and conjunctivitis are commonly caused by environmental allergens that are only present during certain seasons of the year. For example, hay fever is caused by a variety of allergens, including certain grass and tree pollens.

• Allergic Asthma

Allergy can playa part in causing asthma, a condition that affects the small tubes that carry air in and out of the lungs. In someone with asthma, these airways are sensitive and inflamed. Exposure to a trigger makes the airways become narrower producing asthma symptoms - coughing (the most common symptom), wheezing, shortness of breath and tightness in the chest. Asthma should be assessed and treated by a doctor. If you are concerned about asthma, you should consult your own doctor. Although allergic asthma is initially driven by a response to a specific allergen, the subsequent attacks however seem to be perpetuated even in the absence of further exposure to allergen. For example, someone who's allergic to dust might also show hyper-responsiveness to environmental chemical irritants such as cigarette smoke even if the environment is dust free.

• Food Allergy

A food allergy is an immune system response to a food that the body mistakenly believes is harmful. Once the immune system decides that a particular food is harmful, it creates specific antibodies to it. The next time the individual eats that food; the immune system releases massive amounts of chemicals, including histamine, in order to protect the body. These chemicals trigger a cascade of allergic symptoms that can affect the respiratory system, gastrointestinal tract, skin, or cardiovascular system. Although an individual could be allergic to any food, such as fruits, vegetables, and meats, there are eight foods that account for 90 percent of all food-allergic reactions. These are: milk, egg, peanut, tree nut (walnut, cashew, etc.), fish, shellfish, soy, and wheat. Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death.

Treatments

Often, the best way to treat allergies is to prevent them from occurring in the first place; this is accomplished through the avoidance of triggers. When avoidance of the offending allergen is not possible, various medications can treat allergy symptoms. Medications help most people with allergies, but have drawbacks. They have to be taken regularly, cost money and have side effects. Allergy shots offer are the only form of allergy treatment· that actually fixes the underlying cause of allergies.