Allergies occur when the immune system reacts against usually harmless substances in the environment, types of food or drugs (“allergens”). The immune system is extremely complex and so there are many opportunities for things to go wrong. When the immune system reacts against an allergen, an exaggerated, damaging immune response occurs.

Allergic diseases are common and are increasing in prevalence, complexity and severity. They include food, insect and drug allergies, and allergic rhinitis (hay fever). Asthma and eczema may be more severe in patients with allergy and are immune-mediated conditions. The most severe type of allergic reaction is known as anaphylaxis, which is potentially life threatening.

Please note that food allergies are different from food intolerances. Food intolerances are symptoms caused by specific foods but they are not due to an abnormal immune response to the food. Testing (blood tests and/or skin prick testing) can be required to determine whether a food allergy is present but sometimes it is clear cut from the history and testing is not required.

Urticaria (hives) and angioedema (swelling) are conditions of the immune system commonly confused with allergy and can present with somewhat similar symptoms. There can be environmental and drug triggers for these conditions, however the treatment of them is quite different to the treatment of allergy. Therefore, a proper diagnosis is important.

Immunodeficiencies are serious, potentially life-threatening conditions that lead to recurrent infections and, in some cases, cancers if untreated. Primary immunodeficiencies are often due to genetic problems affecting the immune system. They are usually diagnosed in children, who develop very frequent and unusual infections. In adults, primary immunodeficiency may be milder and can therefore be more difficult to diagnose. It is usually detected due to frequent, severe or unusual infections as well. Immunodeficiency may occur as a consequence of treatment for other medical conditions (such as after chemotherapy) in which case it is called secondary immunodeficiency. It will also usually be diagnosed following multiple recurrent infections, which are often unusual, but it may be detected on screening tests in some cases.

An autoimmune disease is a condition in which your immune system mistakenly attacks your body. The immune system normally guards against foreign organisms such as bacteria and viruses. The immune system also has an important role in detecting abnormalities in the body’s cells which if unchecked can lead to cancers. There are many different ways in which the immune system protects us from infection and cancers.

Normally, the immune system can tell the difference between foreign cells and your own cells. In autoimmune diseases, the immune system mistakes proteins found in specific cells in part of your body — like your joints or skin — as foreign. It releases proteins called autoantibodies that attack healthy cells. This can establish an abnormal immune response with recruitment of many other types of immune cells, leading to tissue destruction.

Some autoimmune diseases target only one organ. For example, Type 1 diabetes damages the pancreas. Other diseases, like lupus, can affect many different types of tissue throughout the whole body.

Any tissue of the body can be affected in autoimmune disease, therefore many different symptoms are possible. Autoimmune diseases are frequently treated with medications that suppress the immune system (immunosuppressants) or change the immune system to be less inflammatory (immunomodulators).

There are many autoimmune diseases which are not primarily treated by immunologists, but immunologists may be consulted if there is a lack of response to standard treatments. Many autoimmune conditions can be treated by dermatologists, endocrinologists, neurologists, rheumatologists and ophthalmologists for instance without needing to see an immunologist. However, there are some conditions which are frequently primarily treated by an immunologist especially if they involve more than one system of the body (e.g. skin, nervous system, gut).

Systemic Lupus Erythematosus (SLE) or “Lupus” is an autoimmune disease that can affect any tissue in the body, but confusingly can also be limited, for instance just affecting a single organ such as the kidneys.

The exact cause of SLE is still not known. There is an underlying genetic risk that makes people more at risk to develop autoimmunity. Then an environmental or infectious trigger, or a combination of triggers, stimulates the immune system to start reacting to proteins that should be recognised as self.

SLE cannot be diagnosed on symptoms alone. Some people with lupus may have few or non-specific symptoms.

Vasculitis is a general term for a group of uncommon diseases that feature inflammation of the blood vessels. Vasculitis is characterised by inflammation and damage to the walls of blood vessels which leads to organ disease.

Each of the vasculitic diseases is defined by certain patterns of distribution of blood vessel involvement, particular organ involvement, and laboratory test abnormalities. As blood vessels are found in all parts of the body, many different systems or organs can be affected.

The classic example of an IgE mediated allergy is peanut allergy. The first time a person is exposed to peanut the immune system recognises proteins in the peanut as abnormal and develops specific antibodies to peanut. This is called “sensitisation”. The specific antibodies that form are IgE antibodies and they are a special subset of antibodies that activate a particular group of immune cells called mast cells. When mast cells are activated they release chemicals that produce the symptoms of an allergic reaction.

On re-exposure to the allergen, the immune system produces and allergic reaction. Sometimes the sensitising exposure can be to very small amounts of peanut and may not have been well recognised. IgE mediated allergies can be dangerous because they can occur to very small quantities of allergen in people who are highly allergic. This is why carrying an EpiPen at all times is very important as it is not always possible to be sure that all food is allergen free.

Most IgE mediated allergic reactions will occur very quickly within 1 hour following ingestion but occasionally can take up to 4 hours. The symptoms of an IgE mediated allergic reaction can be swelling of the face, lips or eyes, hives, redness of the skin or abdominal pain, vomiting and trouble breathing.

Anaphylaxis is the most severe form of IgE mediated allergy. Symptoms generally occur quickly after exposure to an allergen but can be delayed in some cases. Anaphylaxis is life threatening and an EpiPen should be used if it develops. The symptoms of anaphylaxis are tongue swelling, throat scratchiness and swelling, difficulty talking, noisy breathing, wheeze, difficulty with breathing, persistent dizziness and collapse, paleness and floppiness in children.

There are a number of common chemicals that the body does not tolerate, but these do not involve the IgE mediated immune response. The symptoms generally develop hours to days after ingestion and are mainly gastrointestinal such as bloating and diarrhoea. Because IgE is not involved, anaphylaxis does not develop. An EpiPen is not required. These reactions generally occur to foods and can be diagnosed on history and then elimination from the diet, rather than from blood or skin prick tests.

In some cases, the diagnosis of a food allergy can be straightforward – for instance if there has been a typical allergic reaction (lip swelling, itchy eyes, throat symptoms, rash) immediately following the ingestion of a type of food that is a common allergen such as peanut, prawns or other shellfish etc. However sometimes this type of reaction can occur when a person has had a meal at a restaurant and is not certain of all the ingredients present, or has had the food many times before, and it can then take some detective work to try to pinpoint whether it was indeed a food allergen or whether it may have been idiopathic (occurs due to an unknown trigger) or another cause of the symptoms.

Environmental allergens such as dust mite, pollen and animal dander, may produce very different symptoms. People may experience a blocked or runny nose (allergic rhinitis) and itchy eyes (allergic conjunctivitis) and may not be able to pinpoint exact triggers. Sometimes people with these symptoms will have been referred by other specialists such as ENT surgeons.

Allergies can also complicate the management of other conditions such as asthma and eczema, and correct identification and management of these can help stabilise these conditions.

Sometimes people have experienced allergic reactions to medications such as antibiotics or anaesthetic agents, and this needs to be confirmed before these drugs can be used again.

Skin testing or a blood test may initially be performed, but in some cases an oral challenge is necessary to be completely sure that an allergy is not present.

After a detailed history and physical examination, it will be clear whether allergy testing is required or not. Skin prick testing is the most common method for testing of IgE mediated allergies (i.e. not intolerances) such as peanut allergy, dust mite allergy, grass allergy etc.

It is important not to have taken antihistamines in the 72 hours prior as this can affect the result.

The testing will occur in the consultation room.

The skin of the forearm will generally be used. The skin is pricked with a disposable lancet for a positive (histamine) control, negative control and the allergens being tested based on the history and likelihood of cross-reactivity. For instance, people with peanut allergy may also be allergic to tree nuts, so these are usually also tested.

It may take up to 10 minutes for a welt to appear around the skin prick, and then the response to the allergen will be measured and recorded.

The results will then be explained and a discussion will occur on what treatment options are available.

You will know if you are seeing a specialist immunologist/allergist as you will need a referral from your GP or other specialist prior to your appointment in order for you to receive a medicare rebate. If you are able to see a practitioner without a referral then you are not seeing a specialist immunologist/allergist with qualifications through the Royal Australasian College of Physicians.

Allergy testing should be the next step in investigation of a person’s symptoms after a thorough history and examination has taken place, as a detailed history in many cases can narrow down the likely allergens that need to be tested. This is important to correctly interpret tests. For some non-immunology practitioners, allergy testing is performed as a “fishing trip” or screening test to see whether a result comes back positive, and whether this then can relate to a person’s symptoms. The reasons that this is problematic is that far more allergens end up being tested than are necessary, which can be costly and confusing. If this approach is taken it is difficult to interpret a positive result. An example of this is a person gets a test done for “tiredness” which includes 30 allergens including to foods that he or she has eaten many times without any problems. Then there is a positive result to “tomato” yet the person has eaten this food for years without any symptoms. This is a false positive result and the patient is in fact not allergic to “tomato”, yet a practitioner with limited training might recommend that the person avoid this food unnecessarily.

Conversely, many people have clear cut food intolerances that will be negative on skin prick testing as they are intolerances rather than allergies, and this in many cases can be diagnosed with a skilful history and does not require expensive testing.

There have also been changes to the Medicare rebates for allergy testing, so that it can will only attract the medicare rebate once per year. Therefore if it is performed by a non-specialist practitioner and then needs to be repeated by a specialist it may not be reimbursed.

Immunodeficiencies are serious, potentially life-threatening conditions that lead to recurrent infections and infection complications. Primary immunodeficiencies are due to genetic problems affecting the immune system. They are usually diagnosed in childhood, due to very frequent and unusual infections. In adults, primary immunodeficiency may be milder and can therefore be more difficult to diagnose. They are usually detected due to frequent, severe or unusual infections as well. Immunodeficiency may occur as a consequence of other medical conditions (such as after chemotherapy) in which case it is called secondary immunodeficiency. It will also usually be diagnosed following multiple recurrent infections, which are often unusual, but it may be detected on screening tests in some cases.

An autoimmune disease is a condition in which the immune system mistakenly attacks the body. The immune system normally guards against foreign organisms such as bacteria and viruses. The immune system also has an important role in detecting abnormalities in the body’s cells which if unchecked can lead to cancers. There are many different ways in which the immune system protects us from infection and cancers.

Normally, the immune system can tell the difference between foreign cells and your own cells. In autoimmune diseases, the immune system mistakes proteins found in specific cells in part of your body — like your joints or skin — as foreign. It releases proteins called autoantibodies that attack healthy cells. This can establish an abnormal immune response with recruitment of many other types of immune cells, leading to disease.

Some autoimmune diseases target only one organ. For example, Type 1 diabetes damages the pancreas. Other diseases, like lupus, can affect many different types of tissue throughout the whole body.

Any tissue of the body can be affected in autoimmune disease. Therefore, many different symptoms are possible. Autoimmune diseases are frequently treated with medications that suppress the immune system (immunosuppressants) or change the immune system to be less inflammatory (immunomodulators).

Some autoimmune diseases are not primarily treated by immunologists, but immunologists may be consulted if there is a lack of response to standard treatments. Autoimmune conditions can be treated by dermatologists, endocrinologists, neurologists, rheumatologists and ophthalmologists for instance without needing to see an immunologist. However, there are some conditions which are frequently primarily treated by an immunologist especially if they involve more than one system of the body (e.g. skin, nervous system, gut).