Why are some people more susceptible to hayfever?

Chris put this question to biologist Sarah Harrison, after asking the panel who suffered from hayfever...

Olivia - I have allergies to a million things so hayfever is just another one on the list.

Chris - Peter?

Peter - No.

Chris - You have escaped.

Peter - I used to have it - I don’t know what happened.

Chris - Your immune system forgot how to…

Peter - Yeah. It’s slightly worrying.

Chris - Simon?

Simon - I’m afraid - I’m drugged up today.

Chris - Another one. I used to get hayfever but it seems to have got a lot better. So, Sarah, are we so unusual. It seems that you have 100% hit rate in the room almost, apart from Peter.

Sarah - Well, I don’t have hayfever, but it does affect what’s estimated to me about a quarter of the people in the world.

Chris - And has that changed?

Sarah - That’s interesting. Pollution levels have been blamed a lot for a hayfever epidemic, if you like, but I don’t think it’s the only factor that increases your susceptibility to this really. It’s hayfever is a type of allergic rhinitis, if you want a more scientific name for it, and this is the same disease that makes you allergic to pet hair and other indoor allergens. It’s not the allergen itself that causes your symptoms as you’re alluded to, it’s the immune systems inappropriate reaction.

Chris - So the allergen is the thing in the environment that you are reacting to like the pollen or the pet hair?

Sarah - Absolutely.

Chris - And it’s being seen by your immune system and that causes the symptom which we call an allergy?

Sarah - Yep. Your immune system recognises molecules on the surface of these little particles and wrongly identifies these molecules as molecules belonging to an invader, and so the immune system reacts to try and clear your body of this invader. That means that you make antibodies and this leads to the cells making histamine, and it’s this chemical histamine that inflames your nasal passages, makes your eyes run and you nose run and everything itch, and makes you feel really terrible.

Chris - This is clearly bad so why should the body allow that to happen?

Sarah - That’s a good question. We don’t really know and there’s a lot of genetic variation in how the immune system works and how it’s set up, so a lot of it is thought to be down to this genetic variation. In fact, it’s a bit of mysterious disease because scientists have only just, in fact there’s a paper last week that pinpointed the real offenders of all the different cell types in the immune system that are causing this allergic rhinitis, and that’s the type of T cell called the Th2.

Chris - So a white blood cell?

Sarah - Yep, absolutely.

Chris - And that cell is the orchestrator of that response is it?

Sarah - Absolutely, as far as we know. As I say, there’s not as much known about it as you might expect for a disease that supposedly affects a quarter of the world’s population.

Chris - Because one highlight, or one thing that’s a recurring theme on this subject is that we’re all living a life that is too clean and sterile and there is this idea of the hygiene hypothesis. We’re not getting enough dirt exposure, not enough stimulation for our immune response and, therefore, it’s sitting there twiddling it’s thumbs and thinks well, I may as well react against something that’s harmless then?

Sarah - Absolutely. And if you don’t have enough of this exposure to this sort of thing in early life it means you never really build up a tolerance to detecting these allergens and the molecules on their surfaces in the environment. It’s also been linked to stress. I don’t know whether Olivia knows anything about this higher susceptibility.

Olivia - You're absolutely right and it’s very true that if you’re feeling stressed. Allergies have actually been linked to poor mental health and, again, we don’t know which comes first. With a lot of things in science it’s the case to this as well. You’re absolutely right. When you’re feeling stressed then your body is a little bit more susceptible and you could react even more to things in the environment that you normally wouldn’t.

Chris - Peter ?

Peter - Yeah I agree. I think everything's connected very much and I think this probably something that’s going to come out more and more over the next few years is the extent to which all of our systems are interconnected. But there is one thing that a lot of these allergies you can actually cure them because really it’s your immune system thinking that this thing is a bad thing that it’s trying to get rid of. I don’t recommend anyone try this at home but, for example, if you’re allergic to cat or dog hair there are treatments by which you eat the allergen. The cat and dog hair goes through your digestive system, and your body’s immune system can actually learn that these things aren’t bad for it. This is a way, for example, you don’t start reacting badly to your meal that you’ve just eaten or something like that. It’s a very interesting balance between reaction and non reaction - you can play with that.

Chris - Indeed. Researchers at Addenbrooke’s hospital in Cambridge at Cambridge University have actually managed to turn people with life threatening nut allergies into people who consume those nut perfectly happily every day by doing exactly as you say. There’s something about the presentation to the immune system of eating something which can familiarise you and abolish the immune response.

Olivia - You know I have exactly tried what you were speaking about and it’s absolutely helped me with my allergies. Also, what I found very useful, and there’s a lot of research on this, for people who have allergies to try an elimination diet where you pretty much eliminate everything you think you might be allergic to. Start with the bare basics, which is exactly what I did, and you work you way up. For example, celery, that was one thing that I was allergic to before. Because some doctors can be quite unhelpful. They just see you for 5 minutes, and that’s about it, and tell you to take more medication. I didn’t want to go down that route so I took matters into my own hands and basically just started off by have a centimetre of celery for two months and just increased that. Now I can have celery.

Peter - Had you been eating much celery beforehand or is it something that you only did very rarely?

Olivia - I’m from Canada, and in Canada my allergies are a lot better than here in England. As much as I love England, I don’t know what it is about the environment here that just makes me sick. I’m okay eating celery in Canada but not here though. Now I am, but not before.

Chris - We should caution people though. If you do have life threatening allergies, do be careful about this sort of presentation approach, because the people who do this in the hospital start with literally amounts that you cannot even see and then slowly scale it up in a safe way. So, it can be done and it is safe if done in the right hands, but do be cautious about just eating things you might be allergic to.