Allergies are very common and increasing in Australia and New Zealand, affecting around 1 in 5 people at some time in their lives. There are many different causes of allergy and symptoms vary from mild to potentially life threatening. Allergy is also one of the major factors associated with the cause and persistence of asthma. Effective prevention and treatment options are available for most allergies.
Allergy – a definition
Allergy occurs when a person’s immune system reacts to substances in the environment that are harmless for most people. These substances are known as allergens and are found in dust mites, pets, pollen, insects, ticks, moulds, foods and some medicines.
Atopy is the genetic (inherited) tendency to develop allergic diseases. People with atopy are said to be atopic.
When atopic people are exposed to allergens they can develop an immune reaction that leads to allergic inflammation (redness and swelling).
This can then cause symptoms in the:
- nose and/or eyes – hay fever (allergic rhinitis/conjunctivitis)
- skin – eczema, hives (urticaria)
- lungs – asthma
A substance that is an allergen for one person may not be for another – everyone reacts differently. The likelihood (or risk) of developing allergies is increased if other family members suffer from allergy or asthma.
What happens when you have an allergic reaction?
When a person who is allergic to a particular allergen comes into contact with it, an allergic reaction occurs. This begins when the allergen (for example, pollen) enters the body, triggering an antibody response. The antibodies attach themselves to special cells, called mast cells. When the pollen comes into contact with the antibodies, the mast cells respond by releasing certain substances, one of which is called histamine. When the release of histamine is due to an allergen, the resulting swelling and inflammation is extremely irritating and uncomfortable.
The most common causes of allergic reactions in Australia are:
- dust mites
- pollen (grass, weed or tree)
- foods such as peanuts, cow’s milk, soy, seafood and eggs
- cats and other furry or hairy animals such as dogs, horses, rabbits and guinea pigs
- insect stings and tick bites
Similar reactions can occur to some chemicals and food additives, however if they do not involve the immune system, they are known as “adverse reactions” rather than “allergy”.
Which areas of the body may be affected?
Depending on the allergen and where it enters your body, you may experience different symptoms. For example, pollen, when breathed in through the nose, usually causes symptoms in the nose, eyes, sinuses and throat (allergic rhinitis). Allergy to foods usually causes stomach or bowel problems, and may cause hives (urticaria). Allergic reactions can also involve several parts of the body at the same time.
The nose, eyes, sinuses and throat
When allergens are breathed in, the release of histamine causes the lining of your nose to produce lots of mucus and to become swollen and inflamed. It causes your nose to run and itch and violent sneezing may occur. Your eyes may also start to water and you may get a sore throat.
The lungs and chest
Asthma can sometimes be triggered during an allergic reaction. When an allergen is breathed in, the lining of the passages in the lungs swells and makes breathing difficult. Not all asthma is caused by allergy, but in many cases allergy plays a part.
The stomach and bowel
Most stomach upsets are caused by richness or spiciness in the food itself, rather than an actual allergy. However, foods which are most commonly associated with allergy include peanuts, seafood, dairy products and eggs. Cow’s milk allergy in infants may occur and can cause eczema, asthma, colic and stomach upset. It may also lead to failure to thrive. Some people cannot digest lactose (milk sugar). This intolerance to lactose also causes stomach upsets, but must not be confused with allergy.
Skin problems such as eczema (dry, red, itchy skin) and urticaria (also known as hives) often occur. Hives are white itchy bumps which look and feel like insect bites. Food may be a factor in some cases of hives and eczema. For more information: www.allergy.org.au/patients/skin-allergy
Life threatening allergic reactions require immediate treatment
Most allergic reactions are mild to moderate, and do not cause major problems, even though for many people they may be a source of extreme irritation and discomfort. However, a small number of people may experience a severe allergic reaction called anaphylaxis. It is a serious condition which requires immediate life saving medication. Some of the more frequent allergens which may cause this are peanuts, shellfish, insect stings and drugs.
If you know that you have a very severe allergy, you should have an Anaphylaxis Management Plan from your doctor, which should include an ASCIA action plan for anaphylaxis. These are available here: www.allergy.org.au/health-professionals/ascia-plans-action-and-treatment
Effective prevention and treatment options are available
Allergen avoidance or minimization relies on identifying the cause of your allergy and then taking steps to reduce your exposure to the allergen. For instance, many people are allergic to dust mites, therefore reducing dust mite in the house is important.
Everything you need to know about allergies
These substances commonly include materials such as pet dander, pollen, or bee venom. Anything can be an allergen if the immune system has an adverse reaction.
A substance that causes an allergic reaction is called an allergen. Allergens can be found in food, drinks, or the environment.
Many allergens are harmless and do not affect most people.
If a person is allergic to a substance, such as pollen, their immune system reacts to the substance as if it was foreign and harmful, and tries to destroy it.
Research indicates that 30 percent of adults and 40 percent of children in the United States have allergies.
- Allergies are the result of an inappropriate immune response to a normally harmless substance.
- Some of the most common allergens are dust, pollen, and nuts. They can cause sneezing, peeling skin, and vomiting.
- Anaphylaxis is a serious allergic reaction that can be life-threatening.
- To diagnose an allergy, a clinician may take a blood sample.
- The symptoms of an allergy can be treated with drugs. However, the allergy itself requires desensitization.
- Anaphylaxis requires emergency treatment. Epinephrine injectors can help reduce the severity of an anaphylactic reaction.
What is an allergy?
Allergies are a very common overreaction of the immune system to usually harmless substances.
When a person with an allergy comes into contact with an allergen, the allergic reaction is not immediate. The immune system gradually builds up sensitivity to the substance before overreacting.
The immune system needs time to recognize and remember the allergen. As it becomes sensitive to the substance, the immune system starts making antibodies to attack it. This process is called sensitization.
Sensitization can take a few days or several years. In many cases, the sensitization process is not completed. The patient experiences some symptoms but not a full allergy.
Allergies may also be seasonal. For example, hay fever symptoms can peak between April and May, as the pollen count in the air is much higher.
The number of people worldwide with allergies is increasing.
An allergic reaction causes inflammation and irritation. The signs and symptoms depend on the type of allergen. Allergic reactions may occur in the gut, skin, sinuses, airways, eyes, and nasal passages.
Allergic reactions may be confused for other conditions. Hay fever, for example, creates similar irritations to the common cold but the causes are different.
Below is a range of various triggers and the symptoms they regularly cause in people who are allergic.
Dust and pollen
- blocked nose
- itchy eyes and nose
- runny nose
- swollen and watery eyes
- swollen tongue
- tingling in the mouth
- swelling of the lips, face, and throat
- stomach cramps
- shortness of breath
- rectal bleeding, mainly in children
- itchiness in the mouth
- swelling at the site of the sting
- a sudden drop in blood pressure
- itchy skin
- shortness of breath
- hives, a red and very itchy rash that spreads across the body
- chest tightness
- possible anaphylaxis
- swollen tongue, lips, and face
- skin rash
- possible anaphylaxis
Anaphylaxis is a quickly escalating, serious allergic reaction that sets in rapidly. It can be life-threatening and must be treated as a medical emergency.
This type of allergic reaction presents several different symptoms that can appear minutes or hours after exposure to the allergen. If the exposure is intravenous, onset is usually between 5 to 30 minutes. A food allergen will take longer to trigger anaphylactic reaction.
Researchers reported in The Journal of Allergy & Clinical Immunology that the most commonly affected areas in anaphylaxis are the skin and respiratory system.
Symptoms of anaphylaxis include:
- hives all over the body, flushing, and itchiness
- swollen tissues
- a burning sensation
- swelling of the tongue and throat.
- a possible blue tint to the skin from lack of oxygen
- a runny nose
- shortness of breath and wheezing
- pain when swallowing
- a drop in blood pressure that can speed up or slow down the heart rate
- abdominal cramps
- loss of bladder control
- pelvic pain similar to uterine cramps
- coronary artery spasm
- low blood pressure leading to high or low heart rate
- dizziness and fainting
Recognizing these symptoms can be crucial to receiving timely treatment.
Causes Of Allergies
A particular antibody called immunoglobin (IgE) causes allergic reactions. Antibodies are released to combat foreign and potentially harmful substances in the body.
IgE is released to destroy the allergen and causes the production of chemicals that trigger the allergic reaction.
One of these chemicals is called histamine. Histamine causes tightening of the muscles in the airways and the walls of blood vessels. It also instructs the lining of the nose to produce more mucus.
The following can be risk factors for developing allergies:
- a family history of asthma or allergies
- being a child
- having asthma
- not being exposed to enough sunlight
- having a different allergy
- birth by Caesarean section
The most common allergens
Potential allergens can appear almost anywhere.
Any food can theoretically cause an allergy. Specific components of food can also trigger allergic reactions, such as gluten, the protein found in wheat. The eight foods most likely to cause allergies are:
- eggs, especially egg-white
- nuts from trees
Other allergens include:
- animal materials, such as dust mite excrement, wool, fur, dander, or skin flakes, as well as Fel d 1, a protein found in cat saliva
- medications, such as penicillin, salicylates, and sulfonamides
- foods such as corn, celery, pumpkin, sesame, and beans
- insect stings, including wasp and bee sting venom, mosquito stings, and fire ants.
- insect bites from horseflies, blackflies, fleas, and kissing bugs
- cockroaches, caddis and lake flies, midges, and moths
- plant pollens from grass, trees, and weeds
- household chemicals
- metals, such as nickel, cobalt, chromium, and zinc
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