Myths of Allergy Testing


We are by no means medical professionals but what we are, are Mom’s who have children with allergies!! My youngest was dairy allergic, soy intolerant and borderline immune deficient as a baby, most of which she has outgrown with a bit of help and my one twin is severely gluten intolerant. Chantal, my Partner’s child, has a variety of allergies, most of which are life threatening and she herself is a Type1 diabetic. So to say we have been there, done that and got the t-shirt is an understatement.

We are here as a support forum. Not to diagnose anyone but to be a shoulder to lean on when you are looking for new allergy free foods or just need some support from a fellow parent trudging your way through the initial diagnosis of an allergy/allergies.

One of the questions we are asked the most, is surrounding Allergy testing. Either because you possibly suspect your child is allergic to something or because your doctor has suggested that you have your child allergy tested. Consult with your Doctor if you suspect an allergy or if your doctor has suggest that you do an allergy test, do it!

If you are concerned about pain, you can purchase an Emla patch. It is a plaster which contains local anaesthetic. You place the plaster on the area where they would be drawing the blood from approximately an hour before. This will numb the area so they won’t feel the initial prick and it has worked brilliantly for all my children. I also always take something with to distract my children, like a treat of sorts they wouldn’t usually have or a favourite toy. For more information on Emla, please consult the information leaflet at and consult with your doctor.

We asked our resident Allergy Specialist, Dr Marinda Macdonald from the Sandton Allergy Clinic to answer a few questions for us below : 

1.  Is it true that you shouldn’t Allergy Test a child before the Age of 12 months old as the results will not be accurate?

It is untrue that allergy testing can not be done before 12 months, as soon as a type 1 allergic reaction appears the possibility of doing a blood test and testing for IgE is possible.This can be done from early infancy, often done this early for a suspected milk allergy. It is true that allergies change as the allergic march progresses, but this by no means that allergies should not be tested for.

2.  Is it better to test for a food allergy with a blood test or a skin prick test.

Food allergies can be tested for by either s-IgE(blood test) or skin test, there are advantages and disadvantages to both. Cost tends to be higher with blood tests, but skilled staff is essential for skin prick test. Components assist with a more accurate diagnosis and this is only available in sIgE. There is no consensus documenting stating preference of one over the other. 

3.  Can you explain the difference between a blood test and a skin prick test and why you would use each of them in different instances?

 A blood test(specific IgE) is a test where the antibodies that are circulating in your blood. A skin test, tests for the IgE antibodies that are bound to cells called MAST cells and their effect. Something like looking into a factory in different sections. Blood tests have the advantage that they are reproducible and can be done while children are on medication or have an eczema flare. Skin tests are fast, immediately available but needs a very well trained professional. Sometimes because of the manner in which the extracts are prepared and patients react it is possible to have a negative blood test and a positive skin test and vice versa. This is very rare. Personally I will not do a challenge unless a skin test have been performed.

4.  Can you Allergy test if the child is taking antihistamines?

Yes, s-IgE (blood test) is not influenced by antihistamines but skin test are.

We would like to thank Dr Macdonald for contributing such valuable information to our website. Should you wish to consult with her, you can contact her on 011 706 1244 /


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