Why is allergy on the rise?

Cause of allergies….

I’m always asked ‘What is the cause of allergies?’ – and it is a difficult question to answer.

Food allergies among children in the US increased approximately 50% between 1997 and 2011 – allergy is now an epidemic in many of the developed countries. And it’s not just children – I’ve also started to increasingly encounter adults who develop food allergies for the first time in their adulthood.


There is no denying that genes play an important role in the development of allergy – if you have a family history of atopy (food allergies, asthma or hay fever) you are more likely to develop allergies but the rapid rise in the incidence of allergy must be linked to the environment too as our genes cannot evolve that quickly.

  • foreign-born Americans have significantly lower risk of allergic disease than U.S. born Americans.
  • your risk of developing allergies increase the longer you reside in the U.S.

In 2013, Dr Silverberg of St Luke’s-Roosevelt Hospital Centre in New York found that foreign-born children who moved to the U.S. had an increased risk of developing allergies, and this risk increased the longer they resided in the U.S. So this supports the theory that environmental factors are causing more allergies.

     Why is the environment making us more allergic?

Whilst there are many theories out there, so far no one has the definitive answer. There’s the Hygiene hypothesis (that we are too clean and the immune system is not stimulated enough – I’m not a fan of this theory though).

Personally, I believe the gut and the food we eat has a lot to answer for…

All disease begin in the gut – Hippocrates

The father of medicine said this about 2000 years ago – and I think we are only beginning to find out there is truth in his wisdom. Obviously, I don’t necessarily agree that ALL disease starts in the gut. Congenital and genetic conditions that you are born with, for example, do not. However, I am convinced that a lot of chronic medical conditions which are on the rise begin in the gut.

Research has shown:

  • Antibiotic use in infancy is linked to increased odds of developing food allergy in childhood
  • The bacteria found in stools of children with food allergy is significantly different to those of children without food allergy.
  • Beneficial bacteria in the gut produce substances which alter the integrity of the gut barrier to the outside world, and the way the gut presents food particles to our immune system.

The Gut

Did you know that the gut is a major immune organ?

As well as digesting and absorbing food, the gut also plays a significant role in healthy immune function. We are seeing a worryingly rapid rise in allergy and autoimmune diseases (e.g. Hypothyroidism, Lupus, Rheumatoid, MS), and although allergy and autoimmune diseases are different entities, there is a common theme – all of them result from a malfunctioning immune system: in autoimmune disease, the immune system attacks the body itself, whereas in allergies the immune system attacks food/environmental allergens.



The allergy epidemic has gone hand in hand with a period in the developed countries of increasing antibiotic usage, GMO foods, intensive animal farming, pollution, increasing cesarian sections rates, formula feeding, and a low fibre/highly processed foods….just to name a few! For example, you may think you are ok because you don’t take any antibiotics, but the antibiotics that livestock has been fed/injected from intensive farming probably stays in the meat, so you are probably ingesting some antibiotics inadvertently when you eat meat farmed this way, and similarly with milk and dairy products.

Why does it matter? Antibiotics kill bacteria – as well as killing the bad bacteria that causes infection, they also kill the good bacteria you need for health.  There are trillions of bacteria in the gut – weighing around 3 pounds, and these are necessary to maintain normal gut function. A combination of environmental factors listed above has led to an altered ‘microbiome‘ so the good bacteria that performs so many functions from digestion, absorption of nutrients, presenting food particles to the immune system, are absent, and the bad bacteria which release toxins and damage the gut lining, take over.

When the lining of your gut is damaged it becomes ‘leaky’ i.e. toxins from the food gets into the bloodstream and lead to inflammation in the body, and food proteins which would normally stay IN the gut and be digested before they are absorbed leak into the blood stream and hence trigger an allergic response. The immune system doesn’t know what to make of these proteins and if they decide that it is a foe the body becomes allergic to that food.



SO it ALL begins to go wrong in the gut! (in my opinion) 

As well as the gut, food allergens may also be presented to the immune system through the skin – and this is particularly relevant for eczema sufferers where the skin barrier is broken and may explain why infants with eczema have a higher risk of food allergies (good eczema control is particularly important in infants to prevent this theoretical mechanism of food sensitisation). It has been suggested that if your immune system is ‘seeing’ allergens through the skin but not encountering it in the gut as food, an allergy may develop to that particular food when you start to eat it. The LEAP study (2015) conducted by Professor Lack’s team in London has shown that early introduction of peanuts into the diets of high-risk infants can reduce the incidence of peanut allergy developing later on (see my blog post on this next week). So it is important that the gut sees these allergens, identify them as food and ‘accepts’ them early on before the immune system starts playing havoc and misleads the body into attacking it.

For me as a doctor, the rise of allergic and autoimmune conditions is both alarming and frustrating as we are not good at treating them. We have strong and toxic medicines to dampen the immune system with but these can cause serious side effects and we don’t like using them. Apart from these toxic medications, we can only treat surface symptoms without ever getting to the root cause: food avoidance for allergy, painkillers for rheumatoid arthritis, steroid creams for eczema. Somehow this just does not feel like enough and made what was a very rewarding job into a frustrating one.

I really think that Hippocrates was way ahead of his time, and we are only beginning to unlock an important piece of the disease puzzle by looking at the gut. The modern day life assails many assaults on the gut and as a result, we are seeing a rise in conditions which were rare a couple of decades ago.

Watch this space.

In the meantime, look after your gut.

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