If an allergy is suspected, it is important that the condition is accurately diagnosed. Usually, a physician is asking about the nature of the symptoms, when they happen, how often they occur and if anything is trigger them. Advice and treatment for mild allergies with a clear cause is given by general practitioners. If the allergy is more severe or it’s not obvious what type of allergen is triggering the symptoms, they patient should be seen by an allergologist (specialist for allergies) for allergy testing.

The allergologist will be asking the patient to give a detailed account of the allergic reactions, the past medical history, the home and work/ school environment, and relevant family medical history. After a thorough ear-nose- throat examination, usually an allergy test is recommended as the next diagnostic step.

An allergy test will attempt to discover an allergy responsible for an allergic reaction if the cause is unknown. Even if the reason for the allergic reaction is known, the diagnosis need to be confirmed by an allergy test, especially if the allergic reaction was severe. Allergy tests are helpful if there is confusion about whether the allergy problem is caused by an airborne or food allergy or whether it might be caused by an intolerance, sensitivity or non-allergic rhinitis. The result of allergy tests should be interpreted by a board certified allergologist. Allergy tests do not always deliver a clear yes/ no answer. Often the allergy test result is only a clue in the clinical puzzle.

Skin-prick tests

Skin-prick testing is one of the most common allergy tests. It involves putting a drop of a substance onto the forearm. The skin is then gently pricked with a needle. In case of an allergy to the substance, a red bump will appear will appear within 20 minutes. The red bump is often itchy. Skin-prick testing is almost painless and very safe. Antihistamines, steroids and certain antidepressant should be avoided before the test as they can interfere with the results.

Blood tests

In addition to skin-prick testing, blood tests may be used. Specific allergy antibodies can be measured in the blood by using a RAST (radioallergosorbent test). A positive result confirms that the immune system has produced increased level of IgE (antibodies) in response to an allergen, for example grass pollen. RAST is useful when skin-prick testing is impossible or the skin-prick testing showed a wide range of positive responses. A careful interpretation of a RAST result by a board certified allergologist is important because positive results can occur in patients without an airborne or food allergy, and negative tests can occur in patients who do have that specific allergy.

Patch tests

Patch test is used to investigate a type of eczema known as contact dermatitis. A small amount of the suspected allergen is added to metal discs and left in place on the skin for 48 hours and monitored for reaction. The patch test is a simple and very safe form of testing, but in severe cases, blistering may develop as a response to the allergen.

Challenge tests

In a few cases, the best way of diagnosing an allergy is to provoke an allergic reaction by deliberately exposing the patient to the suspected allergen. Challenge testing is always carried out in a hospital setting where a severe reaction can be treated if it does develop.

Elimination diet

In case of a suspected food allergy, the patient may be advised to avoid eating a particular food to see if the allergy symptoms improve.

Symptom diaries

The patient is keeping a record of the symptoms on a daily basis along with details of the factors suspected of causing them. This is helpful to see the relationship between various triggers and the specific allergy symptoms.