One of the most frequent questions that I get asked by people is “why are allergies increasing?”. By this they mean why is the prevalence (the presence of allergies in the general population) increasing?
I read an interesting column by a news reporter in LA a few years ago who thought that there was a mass hysteria induced self diagnosis of helicopter parents of food allergies.
Well this is wrong for several reasons.
It is known that the real prevalence rate of food allergies is in fact increasing at a substantial rate where now 3-5% of patients have physician diagnosed food allergies.
So why the increase?
We used to attribute most of food allergy and allergy prevalence increases to the hygiene hypothesis. The theory distilled down proposes that it is the lack of exposure to pathogens or “germs” that predisposes our bodies’ immune systems to over react to harmless things like peanut proteins, pollens, etc…
It turns out there is substantial evidence to support this theory. We know for example that children who grow up with many older siblings and thereby exposed to more infections are less likely to develop allergies. Similarly, children who grow up with a dog are less likely to develop allergies.
When children do get infections such as hepatitis A, they seem to markedly decrease their risk of developing allergies in general. Have we become too clean and hygienic? Well I am by no means advocating for purposely getting our children sick. But perhaps playing in the dirt every now and then can contribute to our children not developing the tendency to develop allergies.
Behind the complex interactions of our immune system and the environment, there appear to be other factors we are now discovering.
An interesting discovery in the field of epi-genetics has also shed light into this phenomena of increasing food allergies lately. It now appears that if your maternal grandmother smoked, the grandchildren are more likely to develop allergies. Why is this so? It has now been demonstrated that although the DNA and genes do not themselves mutate at a fast enough rate to increase allergies, as complex living beings we have also developed an ability to have a dimmer switch on our genes (i.e. how many of them get turned on and to what level). This gives many species to rapidly adapt to a changing environment without having to rely on the painfully slow process of actually introducing base pair changes in our DNA. Put in another way, our genes are formed from DNA with a four letter alphabet A, G, C, and T. The letters in the alphabet typically do not mutate or “change” in their order. However just like how we have accents in our alphabet there appear to be various accents that can change how we say the words that are spelt out with the addition and removal of various punctuations and accents–this is known as epi-genetic markers.
As such if your maternal grandmother smoked, somehow the gene dimmer switches changes so that future offspring can now better handle a polluted environment. This unfortunately results in some aspects of the immune system becoming hyper active. The dimmer switches are made up of these accents / epigenetic changes.