Allergies and Their Diagnostic Methods
Allergy is a reaction of the over-responsive and over-sensitivity of the immune system to a harmless foreign substance in the body. The foreign substances are referred to as allergens and they vary from a simple drug, certain food substances to plant pollen. Whatever may be the allergen, the immune system gets triggered with excessive activation of basophils and mast cells by a particular type of antibody known as IgE. This leads to rapid inflammatory reaction. Some of the most common allergies conditions include asthma, hay fever, allergic rhinitis, food allergies and some skin allergies.
Allergies run in families too and the tendency of some families to develop allergic sensitization is referred to as atopy. In some cases the allergies might manifest themselves in mild form whereas in other cases excessive reaction might lead to death. There exist variety of screening and examinations to diagnose allergic condition and to take recourse to informed decisions to treat the severe condition.
How can allergies be diagnosed?
Allergies are mostly confirmed either by skin tests or by blood examination. Additionally, before going for the examinations, one must also give due importance to the warning signs and symptoms of the allergic conditions. It is important to know the causative agent of allergy. Allergology that is the study of allergy, also help doctors know about the patient’s condition and thereby suggests type of examinations accordingly.
The laboratory tests include:
Allergen skin test: To ascertain the sensitivity of the body for assessing presence of allergen-specific antibodies, allergen skin test is done. This type of examinations is also referred to as prick testing and punctures testing. Under this kind of examinations, series of tiny punctures or pricks are made under the skin. It is through these punctures that small amount of allergens is introduced into the body. In some cases, it is injected through syringes and needles intradermally. The most common areas in which these pricking is carried out are the inside forearm and at the back. It is said that if the patient is allergic to the particular allergen then within a span of thirty minutes, visible inflammatory reaction will occur. This response will be manifested first by reddening of the skin and then a full-blown hive for more allergy-sensitive patients. The result of this test is measured and interpreted in scale where a score of 4+ implies severe reaction to the substance. However, this test has its own limitations, as it should not be carried out on patients who already have severe skin disease or is on antihistamine drugs. Additionally, a blood test is suggested in most cases if the patient has come with severe anaphylactic reaction condition. Again, this test can be done for several allergens at the same time.
Under skin test, a patch of allergen can also be placed on the skin to determine allergic reaction or allergen responsiveness.
Blood Test: Blood tests are not as sensitive as the skin tests and the most common type of blood tests is ELISA (enzyme linked immunosorbent assay). Other examinations include RAST or an immunoassay capture test.
Radioallergosorbent blood test (RAST): It helps one to estimate the total IgE present in the individual blood serum. The radioallergosorbent method of testing employs radioactive technology and uses anti-IgE antibodies as radioactive isotopes to quantify and measure the levels of IgE antibody.
It is found that the results of the skin tests are faster than the blood test. The skin tests are less expensive too than the blood examinations. However, in a blood test there is only a single prick and blood is taken for testing, whereas in case of a skin test, several pricks are done in the body and that can be painful for patients already suffering from skin diseases. Skin tests should always be done by a specialist.
Provocative allergy testing: This method is most reliable, effective and safe for diagnosis as well as treatment of allergic conditions. The sensitivities of the patients to food, food preservatives, hormones, dust, pollen, environmental chemicals and bacteria can be ascertained. This testing is mainly done through sublingual drops or intradermal injections. This may result in suggestive complaint or the allergen might produce some skin reactions too. These are then attended by trained staff and doctors for further evaluation.