• Question: Why do only some people have allergies and not others.

    Asked by anon-253593 on 13 May 2020.
    • Photo: Amy Mason

      Amy Mason answered on 13 May 2020:

      I’m not sure. I know allergies are basically an overactive immune system – your body is reacting to a foreign substance like pollen or nuts as if it is a harmful threat. I know there are definitely genetic connections to some allergies, but I think there is also an environmental aspect.

      This is something we are still learning about!

    • Photo: Alex Holmes

      Alex Holmes answered on 13 May 2020:

      I’m a bit rusty on my immunology, so other people might be able to give you a better answer!

      But basically an allergy is where your body responds to a foreign object in your body in an over the top way. So, there are some things we want our body to react to, like bacteria and viruses, or if we cut ourselves by accident we want our body to try and heal the area. But we don’t want our body to do that when we eat peanut butter or are around pollen.

      To protect us from objects we need protecting from, the body is constantly making new immune cells that have different receptors on them, some can sense bacteria and some viruses, and because the body doesn’t know what receptors it might need it’s constantly making new receptors just in case and if the receptor isn’t used the body get rid of it. By accident the body might produce a peanut receptor cell which then comes in contact with the peanut and sends a message to your body saying “okay we want to keep this receptor and make more of it!” without the body knowing that peanuts aren’t an issue. So the next time the body has a peanut in it, there’s all these immune cells with peanut receptors on them ready to attack, when we don’t really want that to happen! Whereas in other people their accidental peanut receptor cells might never see a peanut so the body gets rid of them and they don’t develop an allergy

    • Photo: Lucy McGowan

      Lucy McGowan answered on 13 May 2020:

      There’s a lot we don’t know yet about exactly how and why some people have allergies and not others. An allergy is the body’s immune system attacking a foreign substance (something not made by the human body) like food or pollen or soap, even though it’s not really dangerous! There are a number of ideas (called hypotheses) about why allergies might be getting more common.
      The first is called “the old friends hypothesis”: As humans evolved over thousands of years, before modern society, we had a lot more infections with parasites like worms in our tummy. Because of this our immune system developed a whole bunch of cells and responses which are designed to control these big parasites. Now we are lucky enough live in a very hygienic society where we wash our hands a lot more and have safe, clean water to drink. As a result, very few people in Western society have these types of infections nowadays! That’s great, but now we think that the part of the immune system that evolved to attack those parasites is getting confused. It expects there to be dangers like worms, so it starts attacking things like food or pollen because it (wrongly) thinks that these foreign substances might be dangerous. Interestingly, in parts of the world where many people still have worms in their tummy due to poorer sanitation facilities and poorer drinking water, there are very few cases of people with allergies!
      The other idea is called “the hygiene hypothesis”: This follows a similar line of thinking in that over the past 100 years hygiene and sanitation in the Western world have dramatically improved. However our immune systems have evolved over thousands of years to live in a more “dirty” world with more threats from infection. With the rapid increase in hygiene, the immune system might not have had time to adapt to the cleaner world yet. It is thought that by having a lifestyle that is TOO clean, especially in early life, the immune system can’t learn the difference between what is really dangerous, like an infection) and what is foreign but not at all dangerous, like peanuts. Though hygiene is super important, especially at the moment, some scientists think that by removing many of the “real” threats to our bodies (infections), our immune systems have become confused. Interestingly there have been studies showing that people who grow up on farms and who play outside more getting mucky in childhood have fewer allergies. Other studies have shown that people who grow up with siblings that play together in childhood are less likely to have allergies than an only-child or the first-born child (again, kids are more mucky and likely to spread germs between themselves).
      We don’t know which hypothesis is right – I suspect they both are. The immune system is super cool but also super complicated so there is loads we still don’t understand!

    • Photo: Sophie Pritchard

      Sophie Pritchard answered on 13 May 2020:

      Great question! There’s already some excellent answers here, but here’s a website explaining allergies and the fact that we still have a long way to go in understanding them. It also gives a bit of history to our understanding: https://mosaicscience.com/story/why-do-we-have-allergies/. I hope this may be quite interesting 🙂

    • Photo: Sarah Montgomery

      Sarah Montgomery answered on 13 May 2020:

      Hi Amy,

      I guess the simple answer is that we don’t actually know. If we did we might be able to predict who would develop what allergy, which would be really useful! This is something scientists are studying, but there are many things it could be, so we have to investigate all of them.

      For example, it could be to do with your DNA. We study this by reading lots of people’s DNA and finding out who developed which allergies and trying to look for links – this is expensive and quite crude! We would then have to test further by looking for more people with the same allergy and seeing if they have the same kind of DNA we thought was important.

      Another theory which I think is really interesting, is that we’ve evolved strong immune systems that used to have to deal with lots more diseases and parasites. Now we’ve largely gotten rid of all the nasty parasites in Europe, our immune systems might still be looking for something to do, so they start going mad if they see a particular food instead! The cool thing about research is you get to look at these kinds of questions and realise nobody in the world has all the answers.

      Sarah

Comments