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Allergy TestingAllergy, Allergens and Allergic Disorders - Symptoms, Treatment and DiagnosisTesting for allergies can be very difficult as it is not easy to pinpoint exactly what is causing the allergy symptoms. However, it is possible to decide what allergies and irritants someone is exposed to, how they may be caused and what can be done to prevent or treat the symptoms. Different allergies may also respond to different tests, with skin allergies being caused by differing factors such as food intake or environmental allergies. Allergy tests should always be interpreted by a trained professional who will discuss a patients history as well as their current symptoms. Allergy Skin Tests Skin tests are commonly used as they are easy, safe, fast and painless - typically in the form of a skin prick test. The skin prick test consists of placing drops of a possible allergen, for example food, mould, dust etc. on the back or forearm. The skin is then lightly pricked with a special needle to absorb the substance. After a short period of time, 10 to 20 minutes, the area is examined to see if there is any redness or swelling. An examination will normally measure the affected area and if their is a swelling larger than 3mm the test is typically considered positive. An intradermal allergy test may be used when the skin prick test has not worked or provided a conclusive result. An allergen is injected into the outer layer of skin with a fine needle and any swelling that forms is once again measured. Skin tests are normally very over-sensitive and can identify allergens that are not causing a problem at all, so their reliability has been questioned. Skin allergy tests are usually used for drug and insect allergies and in some cases for food allergies. Allergy Blood Test A blood test for allergies is called a Radioallergosorbent test (RAST), where a blood sample is taken from the patient and mixed with the suspected allergen in a laboratory to see if there is any reaction. Blood tests can provide an insight into an allergy but they are typically not as accurate as a skin test. A newer version of the RAST test is available called the ImmunoCap which is used together with a skin test to help determine whether a patient has lost any sensitivity to a food or substance before taking a food challenge test. It is still not as effective as a skin test and further research is being carried out as to its effectiveness in evaluating an allergic persons symptoms and causes. Allergy Food Challenge Test A food challenge test is where increasing amounts of a suspect food is fed to the patient and any reaction is noted or observed. If the patient can tolerate the food up to an amount which equals a typical intake, then the food is usually deemed safe enough to re-introduce into their diet. Other Allergy Tests There are many other allergy tests available, however it is always wise to proceed with caution when choosing a test to take and reviewing the results from an allergy test. If a test gives a long list of foods that might be causing an allergy, or the patient is asked to score their reaction to many foods, then the test is probably not accurate. True food allergies are usually limited to a few foods, with the true number for any person being less than five. Food allergy reactions can also depend on many different factors, such as the state of the food (cooked or raw), the amount eaten, the patients health and so on. A test may indicate a mild reaction but this is no confirmation that the patient will suffer no reaction or a severe reaction in the future. |
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