Question: How do people become allergic to things(eg dairy)

Joanna Barstow answered on 19 Nov 2019:

Good question! I actually have an allergy to peanuts, so I know a bit about this, but really we don’t know yet exactly what causes some people to become allergic to things.

I am allergic to peanuts because my immune system incorrectly identifies a protein in peanuts as a pathogen – something that causes disease. The immune system is trained to spot bacteria and viruses and things like that so it can fight them, but in my case it makes a mistake and tries to fight the peanut protein. If I ate a peanut, my body would launch a massive immune response so dramatic that it could become fatal if not treated, because my airways swell up and make it hard to breathe. This is called anaphylaxis.

One theory is that certain proteins, like the one in peanuts, are more easily mislabelled by the body than others. If a child gets exposed to those proteins in the wrong way when they are very young – for example, through the skin rather than by eating them – then theit body gets confused about what the protein is. That’s just one possible explanation.