One of the most common and frightening allergies is the peanut allergy, and its effect can be seen more and more every day, in everything from school lunches to airline snacks. But where do these allergies come from, and why are they on the rise?

The short answer is: “We don’t really know.” For a longer answer, check out the video above from the American Chemical Society.

Peanut allergies differ from other nut allergies for one reason: Peanuts are legumes, meaning they are more like peas than they are like nuts. Peanuts also pack a chemical wallop few other foods can match—one that lingers in the human body.

People have been eating peanuts for thousands of years. So why is it that we as a species are just now beginning to see an increase in negative reactions? The answer most likely lies in modernization. The very things that have increased our lifespan, including antibiotics and better hygiene, are messing with our bodies, making us more vulnerable to bacterial infections and immune system dysfunctions like allergies. Increased fear of peanut allergies led to public health warnings to avoid exposing young children to peanuts. But as we’re learning now, early exposure to allergens like foods and pet dander may actually help us develop resistance. Find out more in the video above.

Header image from YouTube // American Chemical Society