• Question: Why are some people allergic to things such as pollen or nuts and some people are not?

    Asked by pranay900 to Alexis, Dr D, Jasmine, Mario on 26 Jun 2013.
    • Photo: Andrew Devitt

      Andrew Devitt answered on 26 Jun 2013:

      FAb question! Allergy is really weird. But there are some great ideas out there about why this might be.

      There are interesting bits of information. So for example, did you know that children brought up on farms are less likely to have allergy? Allergy is less common in the developing world? This sort of information has led to an idea called the “hygiene hypothesis” – so the cleaner we are the more likely we are to have allergy. So this is a disease of the new western world where everything is clinically clean.

      People have said ‘a bit of dirt won’t hurt’ and the idea is that if you encounter some dirt, your immune system grows up properly. So it fights real infections and challenges (in the dirt). But if you don’t have this dirt around, you end up fighting imaginary enemies like pollen, animal dander and milk and other things that really aren’t that dangerous.

      Allergy though can also run in families. So there must also be a genetic link.

      Very interesting.

    • Photo: Alexis Barr

      Alexis Barr answered on 26 Jun 2013:

      The simple answer is that people with allergies have a super-active part of their immune system. This super active part is controlled by proteins called IgE. IgE molecules are required to fight infections by some parasites, like tapeworms for example. But in some people, IgE also responds to things like dust, pollen and nuts. This means that when these people are exposed to dust, pollen or nuts they are super sensitive and their immune system overreacts giving cold-like systems (runny nose, sore eyes, itchy skin).

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