This summer is already proving a tricky one for people with hay fever. Pollen counts are rising, and more of us are experiencing symptoms than ever before. But it’s not just pollen. From airborne allergens to the food on our plates, or the chemicals and plants that touch our skin, around 40% of the global population has some form of allergic disease. By 2030, today’s guest reveals, 50% of us will be affected.

Professor Theresa MacPhail is a medical anthropologist and writer who made it her life’s work to understand more about allergy after her father died following a bee sting. Her book Allergic: How Our Immune System Reacts To A Changing World is a detailed, enlightening look at the history of allergies and their growth in line with the industrial revolution.

Why are allergies on the rise? Why is it that 200 years ago, allergies barely existed, yet today we’re even seeing them in our pets and farm animals? These are some of the questions we address in this week’s conversation.

Theresa starts off talking about our immune systems and what actually happens to cause the release of a chemical called histamine – which is responsible for many of our allergic symptoms.

She also covers the main historical theories as to the cause of allergies, from the ‘hygiene hypothesis’ to the ‘farmhouse effect’ and the ‘old friends theory’. Each offers us a potential part of the explanation, but none of them in isolation are able to explain it all.

What we do know is that allergies occur in the

Watch the video version of the conversation here: