Allergy test
Since avoidance of the provoking allergen/s is the best therapy it is vital to identify the offending allergens accurately as soon as possible. In many cases a careful and systemic history combined with clinical examination may provide useful clues to the nature of the potential allergens. Avoidance based on guesswork may cause more harm to the child or adult in question. Allergy tests should be performed quickly to accurately identify the suspected allergen triggering the symptoms.

There are two types of allergy test available:

(1) Skin Prick Test, and

(2) Allergy Blood Test, based on ‘Cap RAST’ performed on a blood sample.

Skin Prick Test: In this test small drops of allergens in variable concentration is placed on the forearm and the dermis punctured with a special lancet. The development of a raised area (called wheal) similar to a mosquito bite appears within minutes and the area surrounding the wheal becomes reddened (flare). The response is compared to negative and positive controls run at the same time. A positive reaction for the allergen is confirmed when the swelling reaches a certain size which is bigger than the negative control.

This test has many limitations. Skin testing is dangerous in highly sensitive patients and there have been fatalities recorded in the past. Patients must stop taking anti-histamines for at least 7 to 28 days (depending on drug) because the drug suppresses the skin reaction causing the development of a false negative result. The skin test is not useful for babies and the elderly. In general skin tests are not useful indicators for food allergies because of the frequent false positive reactions. Skin testing is being rapidly replaced with allergy blood testing.