There are three ways of testing allergies
in children. one is a blood test, second is a skin prick test. and third is an oral food challenge.
In the blood test, we take the blood from the child and we test for any number of antigens
that we suspect that can be causing problems. In the skin prick test, we take the antigen
and we do the skin prick. We prick the skin with all these antigens and we read the results
in 15 minutes. Both the tests have equal sensitivity and specificity. That means the reliability
of both the tests is exactly the same. These tests are not 100%. If the test is positive,
that does not mean the child is allergic to it. They may be sensitized 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 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. We don’t know to be honest, but there are certain families which have the tendency to
develop allergies. They have allergic conditions like cow’s milk protein allergy, various
nuts allergies, eczema, asthma, allergic rhinitis. They are called atopic families. 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 runs in families. Why have allergies have become so common is controversial and we’re not 100% sure why it’s happened. But there are certain factors to blame like
the hygiene hypothesis. What that means is that we have become very hygienic. We try to clean
everything and keep everything 100% bacteria-free. That is apparently not a good thing because
our body has forgotten how to fight against various antigens and bacteria. The body is
now recognising these antigens like normal things which are absolutely fine. The body
thinks that these are foreign bodies and they try to mount a reaction to it. That we think
might have led to the increase in the allergies in this day and age.
Also, we used to eat everything without any problem. Nowadays, there was actually a guidance
which advises mothers, expectant mothers to not to eat nuts and various allergenic food.
That was not a good advice because that has led to an increase in allergies. Now, the
recent advice is to eat everything as much as you can if you’re already not known to
be allergic to that particular substance. Allergy symptoms are different in different
age groups. For example, in a baby who’s only given milk, the development of dry
skin or eczema, if the baby starts to vomit after every feed, is very irritable, constipated or has runny
stools or sometimes passes blood in the stool, these can be symptoms of milk allergy.
For food, it’s very obvious. If you eat that particular food, for example a peanut,
and you start developing redness around the face, itchy throat, you may start to vomit
or sometimes difficulty in breathing. That’s again a very clear symptom of allergy. There
can be some situations in which the allergies are a bit more difficult to diagnose where
you may have gastrointestinal symptoms like chronic diarrhoea or you may have a very dry
skin in which case you may be allergic to something which will have to be tested to
confirm. You may have hay fever and maybe allergic to pollen. That again has to be tested
and that’s the way to confirm that you are allergic to pollen which might be causing
your hay fever. It depends on what food allergy you have.
If you have allergy to milk, that can be two types. One is called IGE mediated and the
other is non-IGE mediated. Non-IGE mediated, you grow out of by the time you’re one to
two years of age. If its IGE mediated milk allergy, then it can take a while. It can
take up to 10 years before you grow out of it. Egg allergy, you grow out of it between seven
to eight years of age. Nut allergy is a difficult one. The chances of growing out of nut allergy
are not that common. If you have a peanut allergy, which is actually a legume, then the chances of growing out of that is 1 is to 10 that is 10%. While if you have a tree nut allergies like hazelnut,
cashew nut, or Brazil nut, then the chances of growing out of it is only 1 in 20, so that’s even less than peanut. Nut allergies
are really difficult to grow out of. There is something called immunotherapy which
is recently being tested. It’s not available via the NHS at the moment. But immunotherapy
is something where we give the substance you’re allergic to in small quantities and we expect
you to develop a tolerance. That’s again in experimental phases at the moment. The treatment is mainly symptomatic. If you have eczema, then we use emollient and steroids
and obviously, the main treatment is avoidance of the allergen. If you are allergic to milk,
then we have to try a different type of milk which does not have the cow’s milk protein.
If you’re allergic to nut, then you avoid those nuts. If you’re allergic to house
dust mite, then you keep the house as dust mite free as possible.
The treatment in terms of medication is depending on the symptoms. If you have asthma, then
it’s treated with the inhalers like, you must have heard of the relievers and preventers, which are usually steroids.
The relievers are some bronchodilators which help to dilate the lungs. The mainstay of
treatment is antihistaminics because histamine causes a lot of problems related to allergy
to we take antihistaminics like Piriton which is chlorphenamine or cetirizine or fexofenadine.
If you have real difficulty in breathing, which is called anaphylaxis in which you can
collapse, the treatment is via adrenaline, which has to be given intramuscularly. Children
with nut allergy who have had breathing problems usually carry what we call an adrenaline auto-injector
like epi pen which is lifesaving.