(Intro)

Do you get the sniffles thanks to hay fever or pollen allergies? And when you eat certain foods, like peaches or melon, does your mouth or throat start to itch, even if you weren’t allergic to fruits as a kid? If that sounds familiar to you, you might have oral allergy syndrome, or OAS. Also known as pollen-food syndrome, OAS is surprisingly common in people who have birch, ragweed, or grass allergies.

Allergies are caused when your immune system mistakenly recognizes harmless proteins, like the ones in dust, food, or medicine, as harmful invaders. Your body tries to protect you, like by widening blood vessels to send in immune cells, or by making a ton of mucus to wash away other potential intruders. But after years of inhaling pollen proteins and having allergic reactions, your immune system might have become overly sensitive to them. That’s when oral allergy syndrome develops, and you might have to start watching what you eat.

If you have OAS, your body might confuse the proteins in certain fruits, vegetables, or nuts for allergy-inducing pollen proteins – so your immune system springs into action. In most people with OAS, the symptoms aren’t that bad. If you bite into an apple or a cucumber, you might have an itchy, swollen mouth or throat for a couple of hours, which will go away without any special treatment. After a little while, those pesky food proteins are either washed away or broken down during digestion, so there’s nothing left to make your immune system freak out!

OAS is usually way milder than straight-up food allergies, because the food proteins that trigger allergic responses normally aren’t destroyed by digestion. So they can stick around in your body and cause a lot more dangerous effects. But for people with OAS, even just cooking fruits and veggies, like cherry pie or steamed broccoli, can get rid of the problem.

When you cook food and add things like heat or acidic ingredients, certain proteins unwind, or denature. And if proteins aren’t in the right shape, your immune system won’t recognize or respond to them anymore so no more itchy mouth!

With certain fruits, peeling the skin off can make a big difference too, because that’s where most of the troublesome proteins are. Now, no matter how delicious fresh produce can be, it’s probably a good idea to avoid anything that causes any sort of allergic reaction. And OAS can feel especially annoying because it doesn’t normally appear until your late teens or early adulthood – after years of exposure to pollen.

So even though you might have grown up loving fresh peaches, celery, or sunflower seeds, well, you might have to find a new snack. Or just skip the produce aisle and indulge in some sweet, baked apple pie.

Thanks for asking, and a special thanks to all of our patrons on Patreon! If you’d like to help us keep making episodes like this, just go to patreon.com/scishow. And don’t forget to go to youtube.com/scishow and subscribe!