An allergy occurs when the body's immune system over-reacts to normally harmless substances (called allergens). These substances may be in the air or in what you touch or eat, including medications. Allergies are often a contributing factor to conditions such as eczema and asthma.
If you are an ‘allergic’ person, and you come into contact with an allergen, your immune system produces a special kind of antibody (IgE). Other cells release further chemicals such as histamine that cause the symptoms you experience when you have an allergic reaction.
A very common indoor environmental allergen is the dust mite — or, to be more precise, its faeces. Pollen, particularly from grass, trees and weeds, is another common allergen, as is animal dander (skin scales or flakes from animals). Metals such as nickel in watch bands or belt buckles, and latex in rubber products are relatively common contact allergens.
A number of foods can also cause allergy: the most common are peanuts, dairy, eggs and seafood. However, true food allergies are not common and most reactions to food are more likely to be food intolerance rather than an allergic reaction that involves the body's immune system. Some moulds and insect bites and stings can also cause allergies.
Cigarette smoke is often considered a cause but it is actually an irritant rather than an allergen. That means it does not cause the allergy, but makes an existing allergy worse.
Symptoms depend on which part of the body is affected. For example, hay fever (also known as allergic rhinitis) affects the eyes and nose, causing sneezing, a runny nose, watery, itchy eyes, irritated and itchy throat and, sometimes, a stuffy, blocked nose.
Allergic contact dermatitis (a condition which is caused by the skin coming into contact with an allergen, such as nickel) is characterised by red, scaly skin that itches where it has made contact with the allergen.
Allergies to some foods, bites or stings can cause urticaria (itchy blisters and weals — raised red, itchy patches on the skin).
There are many causes and symptoms of allergy, so if you think you have an allergy, ask your doctor for advice.
A very severe allergy can cause an anaphylactic reaction, where the person can become very flushed, break out in a rash, have difficulty breathing, suffer a severe drop in blood pressure, and eventually lose consciousness. This is a life-threatening situation and needs urgent medical attention (call an ambulance and tell a member of the emergency services what is happening).
While you do not inherit an allergy directly, you may inherit a tendency to be allergic. Doctors call that being atopic. Allergies start only if you are then exposed to an allergen (things that trigger an allergic response in the body).
Once you develop a sensitivity to an allergen, an allergic response is set off again every time you are exposed to the things to which you are allergic.
If you think you or your child may have an allergy to anything, it is important to talk to your doctor, who might suggest tests such as a skin prick test or a blood test (known as a RAST — a radioallergosorbent test).
In skin tests, a needle is pricked into the skin through a drop of the suspected allergen, usually on the skin of the person's inner forearm or back. The size of the weal on the skin indicates how strongly you are allergic to a particular allergen. As many as 30 allergens can be tested at the same time to help identify the particular substances to which you are allergic.
The most important part of managing allergies is avoidance of allergens.
Allergy symptoms also have specific treatments, including medication and self-care methods.
One of the most common medications used for allergies are the antihistamines. These can be quite successful in controlling allergies and many non-sedating and well-tolerated antihistamines are available over the counter from pharmacies.
Other medications for allergy include decongestant nasal sprays to relieve a stuffy nose, and emollient or corticosteroid creams to help soothe inflamed skin.
Your doctor or pharmacist will recommend the right product for your particular symptoms.
Another treatment for some allergies is immunotherapy (desensitisation or hyposensitisation). This involves a series of injections that gradually increase the exposure to an allergen and stimulate the immune system to develop a resistance to the allergen. This, however, requires regular injections over a long period (up to 5 years, for some types of allergy) until you show no significant allergic response to the allergen. It is particularly useful for allergies to insect venoms, such as bee or wasp stings.
People who have life-threatening allergic reactions need to carry an adrenaline self-injection device (EpiPen) with them at all times and be trained in the correct use of adrenaline. Their parents, partners or caregivers should also be familiar with how to use the EpiPen.
Wearing a medical bracelet stating what you are allergic to can be very helpful for doctors and other health professionals. Always remind your doctor or pharmacist of your allergies before starting any new treatment, including complementary medicines.
To minimise allergies, it's important to identify the substances that trigger your allergy and try to avoid them. Here are some tactics to avoid some common allergens, and help minimise allergy symptoms.
Use dust mite covers on all bedding; wash bedding in hot water (more than 55°C) once a week; air pillows and bedding in sunlight for a few hours each week; if possible, replace wall-to-wall carpets with hard flooring such as floorboards; clean non-carpeted floors with a wet or electrostatic mop rather than using a vacuum cleaner; clean carpets weekly with a vacuum cleaner that has a suitable filter (but vacuuming will increase the amount of house dust mite allergen in the air for 20 minutes or so afterwards, so if possible, ask someone else to vacuum and stay out of the room for at least 20 minutes); dust surfaces with a damp or electrostatic cloth 2-3 times weekly; remove fluffy, stuffed toys from your child's bedroom or wash them weekly in hot water (putting soft toys in the freezer overnight kills mites but does not remove allergen); remove soft, upholstered furniture from the bedroom; select furniture that is upholstered in vinyl or leather rather than cloth; and ensure good ventilation throughout your house to avoid moist air build-up. You can never get rid of all the dust mites in your house, but these measures can reduce their numbers.
Keep the garden free of highly allergenic plants; try to stay indoors at times when the pollen count is at its highest, for example, the early evening; ask someone else to mow your lawn; close your bedroom windows at night to prevent pollen entering; wear wrap-around sunglasses to avoid pollen getting into your eyes; and have a shower and wash your hair at night to wash away pollen you may have ‘collected’ during the day.
Don't keep pets, or at the very least, keep them outside.
Avoid strong soaps, perfumes and household cleansing products that may irritate sensitive skin.
If you have food allergies, know what they are and avoid those foods, taking care to maintain a balanced diet. A consultation with a nutritionist or dietitian can be very helpful.
Make sure you wear footwear outdoors; cover your limbs; don't make sudden moves when bees or wasps are around; avoid strong perfume as it can attract insects; take care in the garden — wear gloves when gardening; and use insect repellant.
Last Reviewed: 01 June 2009