How much of a problem are allergies?
What’s the scale of the problem when it comes to allergies? Katie Haylor spoke to Sheena Cruickshank from the University of Manchester. First of all Katie asked Sheena how prevalence of allergy varies across the world...
Sheena - In the UK we have about one in four of us having hay fever allergies, so they’re pretty common. But worldwide we see a real variation, about ten to 40 percent of the population across the world will have an allergy. And what we tend to see is that it varies depending on whether you live in a more developed part of the world or less developed part of the world. So the more developed the area the more likely you are to have an allergy.
Katie - And why is that, do we know?
Sheena - Well, we don’t fully know but there’s an awful lot of ideas as to why that might occur, but one of the ideas is that it’s about the differences in the environment. It’s the microbes that we’re exposed to, it’s the pollutants that we’re exposed to, and it’s the different germs and things that perhaps live inside us; things like our gut bacteria will be different.
Katie - From a population health perspective, how has this incidence of allergy changed over time?
Sheena - It’s changed massively. We see a real increase; for example we’ve seen a 615 percent increase in anaphylaxis, which is a very severe form of allergy in the 20 years running up to 2012. And year on year we’re seeing more diagnosis and more hospitalisations in the UK, so it’s a really steep increase. There’s evidence to suggest that if it keeps going up like this, by 2025 half the population of the UK will have an allergy.
Katie - Why has this increased so much?
Sheena - You can be a little bit genetically susceptible, but what they know now is that genetics isn’t the only thing and the environment, in some way, seems to be really really important, so it’s something that we’re exposed to in our environment. It could be microbes that we’re breathing in - different types. It could be different pollutants. It could be all sorts of things that are sort of coming together and making our immune system respond in a way that it shouldn’t because what an allergy is is essentially your immune response reacting to something that is harmless that you should ignore.
Katie - Now you’re getting the public involved in allergy research as I understand. Tell us about that.
Sheena - We’re really excited about this. We’ve worked with people with allergies and asthma to co-create an app to gather symptom data across the UK. And what that does is we get different symptoms, and we get a timestamp, and a geolocation. So, for the first time ever, we’re able to see when allergy symptoms start to develop and where you were when that happened.
Katie - And rumour has it that you do have some preliminary findings?
Sheena - Yes, that’s right. We have some preliminary evidence where we’ve been looking at possible linkage between the symptoms and different pollutants because we’ve got very detailed data from Manchester. What we’re seeing is correlation between these symptoms and pollutants, in particular things like NOx which we associate with diesel fuel and also some of the larger airborne particles.
Chris - Sheena why do you think that having a bad air day is associated with certain allergic symptoms? Is it doing something to the mucus membranes: eyes, throat, lungs and so on and those mast cells that Eoin was telling us about?
Sheena - Well, there’s a few ideas that it could be. One thing is that it could be damaging our mucus linings, and then that acts as an extra trigger to alert the immune response and kind of fires the immune response off. Another idea is that actually what it does is it changes the structure of the things that we’re allergic to, so it makes them even more stimulating to our immune response, so there’s quite a few different ideas there. But certainly we do see evidence that if there’s heavy pollution we see a lot more hospitalisations for things like asthma attacks and for other people who’ve got breathing associated difficulties. Diseases like COPD for example we will often see that they will feel a lot worse.