How to test for allergies in children

Written by: Dr Ramnik Mathur
Edited by: Jay Staniland

Allergies have become more common in recent years, though we’re not 100% sure why this has happened. There are certain factors that people believe to be responsible, such as the hygiene hypothesis. This means that in modern times we have become very hygienic, and we try to clean everything and keep everything 100% bacteria-free. This is apparently not a good thing because our body has forgotten how to fight against various antigens and bacteria. The body thinks that these are foreign bodies and they try to mount a reaction to it.


How are allergies in children tested for?


There are three ways of testing allergies in children:

  1. Blood test

  2. Skin prick test

  3. Oral food challenge

In the blood test, we take blood from the child and we test for a number of antigens that we suspect to be causing problems. In the skin prick test, we take the antigen and prick the skin with all these antigens and we read the results in 15 minutes. Both the tests have equal sensitivity and specificity, meaning that the reliability of both tests is exactly the same, which is below 100%. If the test is positive, that does not mean the child is allergic to it. They may be sensitised to it. On the other hand, if the test is negative, that again does not mean that the child can have the substance because they can still be allergic to it.

To confirm the diagnosis, we then do what we call an oral food challenge in which the child is given a substance to eat in a controlled setting in a hospital, with all the resuscitation equipment to hand. If the child is able to tolerate it, then obviously, the child is not allergic to it. On the other hand, if the child develops a reaction, then the child is allergic to the substance. That is the best test that we can do for allergy.


What causes an allergy?


It is not known exactly what causes an allergy, but there are certain families, called atopic families, which have a tendency to develop allergies. They have allergic conditions like cow’s milk protein allergy, various nuts allergies, eczema, asthma, allergic rhinitis. There is something in their genetics which make these children or even adults prone to be allergic to certain conditions.

Most people are okay with nuts, but if you give nuts to these children, they’ll react to it. Their body recognises that a nut is a foreign antigen and they mount an allergic reaction to it. We don’t know what causes allergy but we do know that it is genetic.

If you are concerned about allergies in your child, you can make an appointment with a specialist here.

By Dr Ramnik Mathur

Dr Ramnik Mathur is a leading London-based paediatrician. Practising at a number of reputable clinics in the capital including the Clementine Churchill Hospital he specialises in allergies including asthma, eczema and food allergies and common paediatric problems such as excessive crying, reflux, vomiting, poor weight gain, recurring infections, chronic coughs and diarrhoea. He runs courses for both doctors and nurses and holds weekly general paediatric, allergy and baby clinics.

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