Clinical Immunology and Allergy is an Internal Medicine specialty branch of the Australasian College of Physicians. Specialists in the area may diagnose and treat the following illnesses of the immune system:
- Allergic disorders including food allergy, inhalant allergy causing hay fever, urticaria or hives, anaphylaxis, venom allergy, atopic eczema, and allergic triggers of asthma.
- Autoimmune disorders, such as SLE, Sjogren’s syndrome, Scleroderma, Myositis and Vasculitis.
- Immunodeficiency disorders
- Chronic Fatigue syndrome
- Periodic Fever syndrome
An important part of allergy management is to identify allergic triggers for conditions such as allergic rhinitis (hay fever), asthma and reactions to either insects or food. Allergy testing with skin prick testing or blood tests for specific allergic antibodies helps to direct avoidance measures and possible immunotherapy.
Skin prick testing is a convenient and the least expensive method of allergy testing. The results that are available within 20 minutes improve the accuracy of diagnosis. Skin prick testing is usually performed on the forearm, although the back is sometimes used in young children. A drop of commercially produced allergen extract is placed onto a marked area of skin and using a sterile lancet, a small scratch is made through the drop. This allows a small amount of allergen to enter the skin. If you are allergic to the tested allergen, a small lump (wheal) will appear at the site of testing. The local itch and swelling of a positive reaction normally subsides within 1-2 hours but may require an oral antihistamine, topical corticosteroid cream and an ice pack. Severe allergic reactions from allergy testing in asthma or allergic rhinitis (hay fever) are very rare. Medications with antihistamine like actions (such as antihistamine tablets, some cold remedies and antidepressants) should not be taken for 3-7 days before testing as these will interfere with the results of testing. You should avoid creams and moisturisers on your forearms on the day of testing to reduce the likelihood that allergen extracts will run into each other.
Bloods tests for Immunoglobulin E (IgE) antibodies directed against specific allergens or parts of allergens can be measured. These tests are can be performed when skin conditions such as severe eczema exist, for further risk assessment or when a person is taking medications (such as antihistamines) that interfere with accurate testing.
Patch testing is useful for testing for contact allergic dermatitis, such as that triggered by metals and cosmetic preservatives. Using hypoallergenic tape, commercial standardised allergen paste is applied to the skin, most commonly on the back. The tapes are normally left in place for 48 hours and kept dry for the entire time until the result is read. An eczema-like rash can indicate sensitivity to a particular allergen.
Challenge testing may sometimes be required to confirm a diagnosis when the cause of a severe allergic reaction has not been confirmed or if there is a possibilty that a clinical allergy has resolved. This will normally only be performed under medical supervision using foods or medications with appropriate resuscitation facilities available.
Autoimmune diseases result from the immune system producing an inappropriate response against the body’s own cells and this can result in inflammation and then tissue damage (eg to skin, joints, muscles, blood vessels and cells and organs such as kidney, lung, gastrointestinal tract, heart, brain and endocrine organs). Some autoimmune diseases affect mainly one part of the body (such as autoimmune thyroid disease) and others can affect many parts of the body (such as systemic lupus erythematosus and a systemic vasculitis). Autoimmune diseases are usually diagnosed and monitored using the clinical history, blood tests (autoantibodies, inflammation, organ function) and other investigations such as radiologic and nuclear medicine imaging. Currently there are no cures for autoimmune diseases, although there is a wide range of treatment options (eg non-steroidal anti-inflammatory medications – NSAIDS, corticosteroids anti-inflammatory medications – Prednisolone) or other immunosuppressive medications), which are used depending on the type and severity of the autoimmune disease.
People with an immunodeficiency can have increased tendency of suffering recurrent infections that can lead to organ damage. Immune deficincy can present as unusually persistent, recurrent or treatment resistant or unexpectably severe infections. Blood tests can be used to investigate possible immunodeficiency eg total and specific antibody (immunoglobulin) responses, lymphocyte quantification and function, complement levels and phagocyte function. Treatment can include immunoglobulin replacement therapy, immune modulation and antimicrobial therapies.