Allergies: check-up and skin prick testing

April 2017

To diagnose allergies, an allergy assessment including at least one examination and one session of skin prick, patch or blood tests is essential.

Contrary to popular belief, allergy testing including skin tests can be performed on a child from an early age


Many children do grow out of their allergies, where as adults do not. Allergies can be life threatening and generally debilitating, therefore testing, even on young children is crucial. The current consensus is that these tests can be performed very early, even before 1 year especially if the child suffers from severe respiratory symptoms, episodes of urticaria or oedema.

Skin prick testing


Skin tests are fast, cause very little pain, are reliable and take only 15 to 25 minutes (in most cases) to find out the responsible allergens.
  • A positive test causes redness of the skin similar to the itchy spot left by a mosquito bite.
  • The principle aim of the test is to reproduce an allergic reaction on the skin.
  • A drop of the suspected allergen is placed on the skin, then at the centre of the drop, a tiny incision is made by pricking the skin with a small sharp instrument.
  • A reaction similar to a mosquito bite at the place of the test shows that the allergen tested may be responsible for some of the patient's symptoms.
  • This technique is well tolerated even by very young children.
  • 10 to 20% of positive skin tests do not necessarily mean that the tested person is allergic to the tested allergen.

Blood tests


RAST (radioallergosorbent ) and IgE blood tests are used to investigate increased sensitivity to certain food groups, house dust mite and animal dander (fur). Blood tests are also used when skin prick testing is difficult to perform and or interpret. It is most useful for children under five when there is intolerance to certain foods.
  • A sample of blood from a vein is taken. Analysis of the blood is made looking specifically immunoglobulin E (IgE) the antibody involved in allergic reactions, or the suspected allergen.
  • The blood test does not require any special instructions such as a fasting sample or change in any medication treatment.
  • The tests are very specific to each suspected allergen and it measures the amount of IgE antibody in the blood for the suspected allergen.

Patch testing


Is performed by a dermatologist and useful for detecting allergies in contact dermatitis. It can check for delayed reactions to substances that are in contact with skin.

Oral Food Challenges


An allergist or immunologist, in a controlled environment, under close supervision will give food that that is suspected to be causing an allergic reaction.

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Latest update on July 23, 2013 at 11:50 AM by Jeff.
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