Friday Dr Q&A with Prof Hugo – Skin Prick Test

Prof Hugo Van Bever

Prof. Hugo Van Bever is the Head of National University Hospital’s Pediatric Allergy, Immunology & Rheumatology Department. He is also an active member of the board APAPARI (Asian Pacific Association of Paediatric Allergy, Respirology and Immunology) and has published more than 250 papers in national and international journals. His main research interest areas are paediatric allergy and paediatric respiratory infections.

Marcie Mom: Morning Prof Hugo, today’s questions is on skin prick test, something I always recommend parents to do (in this post).

In a skin prick test, typically a few common food allergens such as egg and milk will be tested instead of all possible food that the child may eat. Why is testing a few of these food allergens sufficient to diagnose if there’s an underlying food allergy?

How often should a child get retested for food allergy? And what type of patients needs to be retested regularly?

Anti-histamines should be avoided before a skin prick test so as to avoid incorrect results (due to no reaction seen when there should be one). What else should a parent take note before bringing the child for allergy test?

Prof Hugo: Because only a few foods are involved in eczema, mainly in young children. These are: cow’s milk, egg, wheat and soy. Other foods are very seldom involved in eczema. In older children food allergy is usually not involved in eczema. Older children have mainly an allergy to house dust mites.

If the child improves there is no need to repeat skin prick test.

Skin prick test should be performed only when the child is in good health (no ongoing infection, no fever) and did not take antihistamines for at least 3 days. Antihistamines may suppress the skin prick test’s results, leading to false negative results. Skin prick test also needs an area of normal skin. In cases of severe eczema, skin prick test’s results are difficult to interpret. A blood test might be an alternative.

Marcie Mom: Thanks, for adults who can take a patch test, can refer to this post.

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  1. It’s a confusing issue. There can be true allergic reactions to foods (I was not aware that so few were involved) as well as reactions that are not related to antibodies–triggers such as spices and histamines in fermented food. The more processed food you or your kid eat, the harder it is to figure out what the main causes are, if indeed the primary problem is with food.

    I didn’t know, either, that antihistamines could cause problems with a skin prick test. I only wish that antihistamines actually worked to reduce itch reaction (I’ve personally found Claritin and Allegra useless, even against reactions that I assume are caused by histamines.) Perhaps Dr. Van Bever could explain why antihistamines are generally ineffective for treating eczema.