Allergies: A Brief Introduction

by Farzana Rahman

Allergies are Everywhere

Gluten free

Dairy free

Meat free

Lactose intolerant

Nut allergy

Allergic to shellfish

Allergic to dust

 

It seems that the list of allergies and intolerances around us are increasing. But is this a real phenomenon or a fad? Dr Alexandra Sontos is a Senior Clinical Lecturer at the Department of Paediatric Allergy, King's College London and wrote a great analytical piece for the BBC on this recently. We dissect the main points from the article in the post below.

 

Food Allergies are Actually Increasing

There has been a rise in recent decades, particularly in the West.  The stats are very interesting:

  •      Food allergy affects 7% of children in the UK

  •      9% of children in Australia have food allergies

  •     2% of adults in Europe have allergies

Children are also far more to develop food allergies than before. Allergies can have serious consequences. Anaphylaxis (an extreme response to an allergy) can cause lip swelling, skin rashes and swelling of the airways which can, at its worst, stop breathing.

 

Causes of Allergies

An allergy is caused by the immune system going into overdrive. It begins to fight substances in the environment that it should see as harmless, known as allergens. The immune system sets of chain of reactions in the body which manifest as allergic reactions.

Symptoms of allergies include skin rashes, swelling and watering of the eyes (hayfever is a good example of this). In severe cases, allergic reactions cause vomiting, diarrhoea, and anaphylactic shock.

The most common foods that children are allergic to include:

·       Peanuts

·       Milk

·       Eggs

·       tree nuts (eg walnuts, almonds, pine nuts, brazil nuts, pecans)

·       sesame

·       fish

·       shellfish (eg crustaceans and molluscs)

 

Is Everywhere Allergy Prone ?

It seems that the frequency of food allergies has increased in industrialized countries. Peanut allergies have increased five-fold in the UK. As we mentioned before, Australia has the highest rate of allergies in the world.

An important question to consider is whether there is truly an increase in the prevalence of allergies or whether we’re just better at diagnosing them.  The researchers seem to think the former is true, namely that the prevalence of allergies is actually increasing.

 

 

Causes of Allergies

Researchers hypothesize that the increased prevalence of allergies is related to environmental factors and Western lifestyles. Interestingly, there are lower rates of allergies in developing countries.  What’s fascinating is that migrants show a higher prevalence of asthma and food allergy in their adopted country compared to their country of origin.

 

Possible causes of allergies include:

  • Pollution: Cities such as London have terrible air quality which can cause chronic inflammation of our airways.

  • Less exposure to microbes: We’ve done some more in-depth posts about understanding microbes here.

  • Dietary changes: the variety of food in diets is changing. Some children are less likely to be exposed to a large variety of food

  • Hygiene: This is a huge factor. Children get fewer infections, particularly parasitic infections such as worms. Whilst we think this is a good thing (how could we not), this could be inadvertently causing allergies.  With fewer parasites to fight, the immune system turns against things that should be harmless.

  • Vitamin D: There is a theory that vitamin D helps the immune system regulate itself in healthy way. The awareness of risks such as skin cancer together with a general trend of spending less time outside, means that most people around the world do not get enough vitamin D.

  • Timing: There’s an idea that food allergy development is down to the balance between the timing, dose and form of exposure.  Eating trigger foods during weaning can help babies have a healthy response and prevent allergy development. King's College London's LEAP Study, showed about an 80% reduction in peanut allergy in five-year-old children who regularly ate peanut from the year they were born.

 

Going Forward

It’s difficult to get rid of an allergy once you have one.

As a society, our preoccupation with hygiene seems to have backfired on us to a degree. However,  it’s also worth remembering that improving hygiene through intiiatives such as handwashing have had a huge impact on childhood mortality from infectious diseases in developing countries.  There is a balance to be had though. Getting outside and trying different foods could help curb the tide of rising allergies in children.

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