Allergies to nuts, grains, vegetables, seafood and milk are common. Allergies to meat? Much less so. But that’s starting to change.

A few months ago I read about adults (author John Grisham in particular) developing an allergy to red meat after being bitten by ticks.* And not just a low-level allergy like your face turning red — we’re talking full-on hives and anaphylactic** shock, the kind of thing that requires you to carry an Epi-Pen to make sure you keep breathing long enough to reach the emergency room.

Researchers have determined that the lone star tick’s bite can cause the body to produce an IgE antibody for a sugar called alphagal, which is found in mammal meat.

The result: from then on, you’re allergic to meat.

CNN calls it mysterious. Allergic Living calls it baffling. It’s certainly weird compared to “usual” allergies, and the fact that the reaction is usually delayed by a few hours makes it hard to diagnose, but we’re ahead of the game in understanding it: Unlike most allergies, we know what causes this one.***

With most allergies, we know the process, but we don’t know what gets the ball rolling to begin with. We know that in people who are allergic to a food, exposure to it causes an IgE antibody reaction that triggers a massive release of histamines that sends the body into some level of shock, but we don’t know why some people have that reaction and others don’t.

There are a lot of ideas being investigated, with varying amounts of supporting evidence, but there’s still nothing we can point to and say: “This caused you to be allergic to nuts” or “That caused you to be allergic to milk.” Advice to parents concerned about keeping their child from developing allergies is all over the map.

That’s why Katie and I are walking in this year’s Walk For Food Allergy. The event raises money for the Food Allergy and Anaphylaxis Network’s mission to support allergy research, spread awareness (you’d be amazed at how many people dismiss allergies as inconsequential or even bogus), provide education and advocacy for people living with food allergies.

Walks are being held across the country over the year. We’ll be walking in the Los Angeles event in October. If you’d like to help, you can donate or join our team here: [Edit: link removed since the event is over.]

Thank you!

*Naturally, this was a few days after I hiked a severely overgrown trail without taking precautions against ticks, so I freaked out a bit, but I also hadn’t found any ticks when I got home from the hike.

**Fun fact: Chrome’s spell-checker doesn’t know “anaphylactic,” and suggested such helpful alternatives as “intergalactic” and “anticlimactic.” Not sure about the former, but I get the impression a lot of viewers suffered “anticlimactic shock” when watching the Lost finale.

***Or at least we know what primes it. There’s still the question of why only some people who are bitten by the lone star tick go on to develop the allergy.