The immune system is a mysterious thing. Protective overall, and yet sometimes it backfires. A dramatic illustration of the immune system going wrong was the TGN1412 disaster: six young men given a monoclonal antibody in a clinical trial ended up in ICU with multiple organ failure. One is now showing signs of an aggressive cancer.

Less dramatic, but more aggravating to more people on a more regular basis, are your run-of-the-mill allergies. Almost everyone I know is allergic to something: peanuts, cats, dust, pineapple. I personally have some mild allergies to some animals, but a major reaction to dust mites. When I got an allergy skin test, the swelling that appeared in response to dust mites moved beyond the realm of a few millimetres, which they usually measure, and looked disturbingly like a fat worm under my skin.

It’s bewildering, too, the different things that people say about what causes allergies. It seems that no one can agree on whether it’s over- or under-exposure to the allergen that causes the immune system to go nuts and attack a harmless molecule. Now it’s been suggested that the window of opportunity for avoiding the nastiness of an allergy is pretty small: sometime between six months and nine months of age, at least for food-related allergies.

Personally I don’t think there’s a straight answer to this one and it just highlights the intricacy of the body, which can work against us or in our favour, but is fascinating regardless.