Allergies are much more than a minor inconvenience. If left untreated, allergies can lead to many chronic illnesses, including asthma, sinus infections, upper respiratory infections, ear infections, and general susceptibility to disease.
Airborne allergens, food, or chemical substances can trigger allergic reactions and intolerances. These could be from dust mites in your bedding, tree pollens in the summer breeze, or sesame seeds on your roll.
If you are concerned about your allergies, allergy testing is the first step towards finding relief. It is necessary to identify the cause of an allergy so that the most effective treatment plan can be implemented.
When Should You Have An Allergy Test?
Allergy or intolerance tests are recommended if you have asthma, hay fever, or reactions to certain foods or chemicals.
Allergic reactions to food often include symptoms such as hives (raised rashes), swelling, vomiting, and diarrhoea. Some people have severe food allergies, which can result in a life-threatening condition known as anaphylactic shock.
People with asthma may experience wheezing, chest tightness, shortness of breath, or a cough. At the same time, hay fever sufferers may have symptoms such as itchy or watering eyes or an itchy, blocked nose (a kind of hay fever known as allergic rhinitis).
Skin Prick Test
Skin prick tests are the most common and accurate way to test for allergies. Tiny droplets of inhaled (airborne) and food allergens are applied to the skin, and the skin is then lightly pricked. If you are allergic to any of the applied allergens, an itchy, raised red bump (the size of your little finger) will appear. This process is not painful, and results are usually available immediately after the test.
Skin prick tests can check your reaction to grass pollen, maise pollen, dust mites, cockroaches, cat hair, dog hair, and mould. Food allergy skin prick tests include milk, egg whites, peanuts, soy, fish, and wheat.
The advantage of skin prick testing is that it is relatively cheap. Results are highly accurate and available almost immediately.
Skin tests are more accurate than blood tests, but people with skin conditions cannot use allergy skin tests because their condition might confound the results of the test. Blood tests cover a wide range of allergens. A single blood sample can process numerous allergens. You can continue taking medication when undergoing blood testing for allergies.
Blood tests measure the immunoglobulin E (IgE) antibodies in your blood. IgE antibodies are produced when your body reacts to substances you might be allergic to, such as specific foods. There are two main types of blood tests, namely:
- The ImmunoCAP Specific IgE blood test is the most sensitive and accurate blood test available. It can detect up to 112 allergenic components in one test, including airborne, food, and stinging insect venom allergens.
- The older RAST test detects antibodies against various allergens and sensitises to more than 400 food and airborne allergens, but these need to be tested one at a time.
This test is considered the “Gold Standard” for allergy testing. During this test, you are exposed to the suspected allergen in a controlled manner. Consuming even a tiny amount of peanut butter can trigger an allergic reaction in sensitive individuals, such as experiencing an itchy or swollen mouth. Therefore, challenge testing must be carried out in a medically supervised environment to ensure safety and accuracy.
During a food provocation test, increased concentrations of a suspected food allergen are given. The first step involves holding the suspected allergen in your mouth and then spitting it out. Then, the food is eaten, in gradually increasing amounts, to determine how much of that food can be tolerated.
A drug allergen challenge test is used to exclude allergies to medications such as penicillin or local and general anaesthetics. This test is done in the hospital under close supervision. Tests include several stages of skin prick, intradermal, and provocation tests.
Food Intolerance Tests
Lactose and fructose intolerances result from the inability to digest the sugar in cow’s milk (lactose) and/or the sugar in fruit (fructose). These intolerances often result in abdominal pain, flatulence, and diarrhoea shortly after consuming these foods. A breath hydrogen test is often used to detect fructose or lactose malabsorption. This test measures hydrogen levels in your breath after consuming a particular sugar.
Gluten is a protein found in wheat, rye, and barley. If you are gluten intolerant or have coeliac disease, you may struggle with several troublesome symptoms, including stomach pain, bloating, flatulence, diarrhoea, malabsorption (with anaemia), and recurrent mouth ulcers. Two blood tests can help diagnose gluten intolerance. Serology tests look for antibodies in your blood. Elevated levels of specific antibody proteins indicate an immune reaction to gluten. Genetic testing can be used to rule out coeliac disease.
Other Allergy Tests
Less common but beneficial tests that can also be performed include:
- Patch Test: Also known as an epicutaneous test, this allergy test detects delayed reactions to chemicals, perfumes, metals, and other allergens. It is usually done for allergic contact dermatitis and other conditions where delayed hypersensitivity is suspected.
- Intradermal Test: This is a form of skin prick testing, where a trace of the suspected allergen is injected into the skin. If allergic, the injection site will itch and turn red. This test is mainly used in antibiotic and local anaesthetic allergy testing when the skin prick test is negative, but an allergy is suspected.
- Nasal Provocation Test: This test is used to confirm an allergy to a specific allergen when other tests have given uncertain results and doctors suspect a localised allergic response (i.e., not systemic).
- Serum Tryptase Test: This test is usually used to confirm a diagnosis of anaphylaxis. This test is useful because histamine is rapidly metabolised and challenging to measure in the blood, while the tryptase levels last for six hours in the bloodstream after an allergic reaction.
Frequently Asked Questions
An allergy is a condition in which the immune system reacts abnormally to a foreign substance.
When the airways are affected by an allergy, asthma symptoms (like coughing, wheezing, or trouble breathing) can occur. Common allergens that cause allergic asthma include dust mites, cockroaches, pollen, mould, and pet dander.
An allergist is a doctor who specialises in diagnosing and treating asthma and other allergic diseases. Allergists are specially trained to identify allergy and asthma triggers.