General Paediatrics, Asthma and Allergy

Dr John Chapman   FRCPCH
  Consultant Paediatrician (NHS & Private)

Making sick children better.

Frequently Asked Questions

What is an Allergy

An allergy happens when your body's immune system over-reacts to something that most people would tolerate. It might be a food, something that you touch or something that you breathe in.


Our immune system is a collection of different processes in our bodies that are designed to protect us from bacteria, viruses, fungi and worms which try to get into our bodies by various means. To do this, your immune system needs to be able to recognise what is part of your body and what is foreign to you. It should also be able to recognise which of these foreign things are harmful and which are harmless. If you have allergies, this is where things go wrong.


How do we get allergies?

Our immune system is looking at millions of different things every day and trying to work out where it should focus its efforts. Sometimes it gets the focus wrong and decides to launch an all out attack on something that would never harm us - like a peanut or a tiny piece of pollen. Once your immune system has made up its mind that something is bad for us, it is very difficult to persuade it otherwise.


What happens in my body during an allergy?

When you come into contact with something foreign to you, your immune system takes a look at it. If it has previously decided to treat it as a potential invader, it will send out specialised immune cells and chemicals to attack it. Because there is no danger and nothing to attack, these cells and chemicals just cause damage to your own body’s tissues which are caught in the crossfire. The chemicals used in the attack are very potent and they cause swelling, redness and irritation.


If this attack happens in your skin, you will get swollen, red itchy lumps called Urticaria (which is the Latin name for the stinging nettle plant) hives or wheals. If it happens a lot in the same part of your skin, you will get a more long-standing reaction like a dermatitis or eczema.


Now, imagine this reaction happening up you nose (Hay Fever or allergic rhinitis), in your lungs (asthma) or in your stomach and gut (food allergy). 

 

Most of the time this reaction stays locally in the tissues but sometimes it can set of a larger reaction which effects the whole body, the larger breathing airways and the blood circulating system: this is called anaphylaxis (ana-fil-axis) which can be fatal.

Why are more children getting allergies?

Why does this happen? Good question, and why are we seeing more asthma, allergies, eczema and anaphylaxis nowadays.

 

Well, our immune do systems were designed in the olden days when we ate unwashed, uncooked food and lived like animals (or with our animals) in a much dirtier environment. It seems that we are now too clean and sterile for our own good.

 

Unfortunately, our immune systems haven't kept up with the good news about our improved healthier life circumstances. It is still on “Red Alert” for invaders 24/7.

As well as outside bacteria, our intestines are full inside with a huge variety of bacteria. Our immune system will keep looking at this bacteria and that seems to keep it busy and happy enough. Check out the TEDx video above.

 

In the last few years, it has become increasingly evident that this store of bacteria is important in preventing allergies. There are usually thousands of different types of bacteria in your gut. This variety is important; perhaps more important than the total bacteria number or count.

 

Studies have shown that children with allergies have lower gut bacterial variety (reduced intestinal microbionta).

So, how do children end up with reduced bacterial variety?

 

Firstly, they can miss out on vital opportunities to collect bacteria. Babies born normally swallow bacteria on their way through the birth canal. If a Caesarean section is performed, this opportunity is missed. Children born by Caesarean section are more likely to have allergies.

 

Breastfeeding is another good source of bacteria and bacteria promoting compounds (pre-biotics).

 

Babies who are brought up in a less sterile environment seem to have less allergies. Babies brought up on farms or who have dogs have less asthma.

 

Secondly, children can have have their gut flora reduced by antibiotics. Antibiotics after all are designed to kill bacteria and when we take them by mouth for an infection as well as killing the bacteria causing the infection they will also kill some species of gut bacteria reducing the overall numbers and the variety.

 

Much of the immune systems decision making seems to be done by the age of about four years old. For example, the children of immigrants who are born in, or come to the UK before the age of four years old have the same levels of asthma as the native UK population even if they come from a country with a much lower incidence of asthma. We do something in the UK which gives more of our children asthma (and probably allergies) than other countries.


Read about Allergy Testing


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