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A person, who is overly reactive to a substance that is well tolerated by most other people, is said to be allergic, or atopic.

The substance which causes an allergic reaction is called an 'allergen'. An allergic reaction causes the immune system to over-react to the substance. Antibodies are produced within the body to identify and destroy allergens. Allergic reactions occur when there is an overproduction of an antibody and the immune defences act too strongly against an allergen. The antibody binds to certain cells (mast cells) found mainly in the skin and lining of tissues of the body such as in the nose, lungs and gut.

When an allergen is inhaled or eaten, the mast cell is activated to release substances called mediators, such as histamine, to combat the allergen. Histamine and other mediators cause inflammation and tightening of the airways. Antihistamines are drugs, which help to block this reaction.

Intolerance vs allergy
Many food intolerances are mistaken for allergies. A food intolerance is an adverse food-induced reaction that does not involve the immune system. Food intolerance may cause symptoms such as gastrointestinal problems (e.g. diarrhoea or constipation. Lactose intolerance, for example, is due to difficulty digesting the sugar in milk and is also not an allergy.

Most allergens are found in the atmosphere and may include cigarette smoke, dust, pollen etc. Other allergens include food, insect stings, medications and latex; in fact anything which the body may regard as 'foreign'.

There are 4 main types of allergens. These typically include:
• House dust mites
• Other components of house dust such as food materials and fragments from insects
• Pollens from grasses and weeds (causing hayfever)
• Spores from moulds
• Cigarette smoke
• Air pollution
• Animal hair/fur

• Cow's milk
• Wheat
• Eggs
• Nuts
• Seafood
• Soya beans
• Drugs such as penicillin
• Naturally occurring or added food chemicals, such as salicylates, amines and glutamates.

• Insect bites or stings
• Injections of antibiotics (the most common being penicillin) and vaccines. A more serious allergic reaction called anaphylaxis may occur which can be fatal if not treated promptly.

Contact allergens
• Allergies occur when the following come in contact with the skin:
• Plants
• Industrial chemicals and those used in handiwork and other hobbies such as glues and solvents
• Some cosmetics
• Jewellery.

Whenever an allergic reaction occurs, there is tissue (cell) injury. Depending on the allergen and where it enters the body different symptoms may be experienced. Pollen, for example, when breathed in through the nose, may cause symptoms in the nose, eyes, sinuses and throat. Anaphylaxis is the most severe form of allergic reaction. It results in potentially life-threatening symptoms such as difficulty breathing, hives, stomach upset or a drop in blood pressure (shock).

General allergy symptoms
• Nasal congestion
• Coughing
• Wheezing
• Itching
• Shortness of breath
• Headache
• Fatigue
• Hives and other skin rashes.
• Food allergy symptoms
• Swelling of the tongue and throat
• Difficulty swallowing
• Nasal congestion
• Difficulty breathing
• Runny or itchy nose (rhinitis)
• Hives or skin rash
• Vomiting
• Abdominal cramps
• Diarrhoea
• Wheezing (this often sounds like the wheezing associated with asthma)
• In severe cases: drop in blood pressure, loss of consciousness and respiratory failure (anaphylactic shock).

It is important to consult your Doctor to diagnose and treat this ailment. Food and chemically induced allergies can be difficult to identify. Your doctor may refer you to an allergy specialist to identify the cause. This specialist can accurately diagnose an allergy by a blood test or skin prick test. The severity of the allergy is assessed according to the test result and the person's clinical history.

Note: Allergic responses to certain foods can cause very serious symptoms. It is essential to identify allergenic foods so other more serious problems do not arise. Your doctor may refer you to an allergy specialist.
• Avoid foods that are most commonly associated with allergic reactions, such as peanuts, cow's milk, soya, seafood and eggs. Similar reactions can occur to some chemicals and food additives.
• Fortunately, the majority of food allergies are not severe, and will disappear with time, particularly in children. Allergies to nuts, seeds and seafood, however, tend to persist throughout life.
• In some cases, a temporary 'elimination diet' under close medical supervision will be needed. Potentially allergic foods are eliminated from the diet then reintroduced to help identify the cause of the allergic reaction.
• Carefully read the content labels of foods in supermarkets. For example, the terms 'whey' or 'casein' would indicate the presence of dairy products.
• Prepare in advance for eating away from home as this poses greater risks. For example, it is wise to inform your host or restaurant chef about your allergy and the importance of avoiding contamination of your meal with an allergen.
• It is important to discourage a child with a food allergy from swapping food with friends.
• You may need to provide special party food for your allergic child to take to parties.
•Relatives, baby-sitters and other caregivers need to be warned about the problem.

Avoid house dust by replacing carpet with polished boards, linoleum, cork or slate; vacuuming regularly, storing books and dust catching items out of living areas and replacing curtains with plastic blinds.
Watch for allergic reactions to pets, especially cats. Remember that cat saliva, which is an allergen, remains suspended in the air for up to six months.

1. Try to identify the source of the problem and make every effort to avoid any known allergens.
2. Your pharmacist may suggest an antihistamine. Ask about any possible side effects, which may include drowsiness. Tell your pharmacist if you are pregnant or breastfeeding. .
3. If the allergy has caused a rash and the skin is not broken, ask your pharmacist for an antihistamine or mild steroid cream.
4. If you suffer from pollen inhalation, consider staying indoors between the hours of 6 am and noon, when pollen is at high levels in the atmosphere. Wearing a mask and sunglasses while mowing or working in the garden may provide protection while you are working in the garden.

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