The curious case of spontaneous allergies to meat. It could happen to you.
Today we’re going to engage in a creative hypothetical, and you, my reader, are the protagonist. I’d ask you to close your eyes and let your imagination wander, however that might be counter-productive considering this is a blog. So maybe just read on:
You’re out for dinner at a Michelin-star restaurant specialising in meat dishes. That’s perfect, because you happen to love meat. Umming and ahhing about whether to go for the Mexican spiced rib eyes with lime butter, or the French wild-boar bolognaise with gnocchi, you decide to stay safe and stick with the former. It’s absolutely scrumptious. You rave about it in your Instagram story and head home a satisfied customer.
Yet that night you feel awfully sick. Light-headed, a bit nauseous, you break out into rashes. Confused at this seemingly random allergic reaction, you dismiss it as a one-off.
Two weeks later, just hours after slamming a late-night Hungry Jacks Whopper in the city, you head home and suddenly feel like fainting. The exact same symptoms as the week prior arise.
The next morning, anxious, you visit your GP and field your hunch: “do I have an allergic reaction to meat, doc?”
The doctor, at first appearing slightly bemused but then breaking out into full-blown raucous laughter, dismisses your claim with a wave: “You can’t suddenly become allergic to meat!”
**End of creative hypothetical**
It turns out though that this hypothetical is all too real for many people. People who have eaten meat their whole life, suddenly experiencing allergic symptoms to their favourite dishes.
In 2002, after some medical detective work, researchers in the US discovered that these patients were specifically allergic to galactose-alpha-1,3-galactose, or “Alpha-gal”. This carbohydrate is found in the blood of all mammals except for humans and a handful of other primates. Consequently, when these allergic patients ate mammalian meat (e.g. beef, lamb, bacon) their bodies reacted to the Alpha-gal molecule and it made them sick.
But why the sudden allergy?
Mapping incidents of the allergy, the researchers found a correlation between where the patients lived and the ecological range of the Lone Star Tick (Amblyomma americanum) – as in, a little parasitic critter with claw-like legs. To confirm the connection, they asked the patients: had you recently been bitten by a tick before the allergy arose?
The answer: yes.
When the tick bites, it transfers a dose of Alpha-gal in its saliva across the human skin and into the blood. The theory is that as the body’s immune system begins to attack the tick’s saliva molecules, it recategorizes Alpha-gal as a harmful substance at the same time. So the next time the victim eats meat and ingests Alpha-gal, the body freaks out and produces heaps IgE antibodies to attack the carbohydrate.
It is the build up of antibodies that causes the allergic symptoms.
Unfortunately for Aussies, we have our own version of the allergy-causing tick – Ixodes holocyclus, the Australian paralysis tick. In fact, cases of mammalian-meat allergy have been reported all around the world. But not to worry (too much), prevalence in the local Sydney Basin is only 113 cases in a 100,000.
If those odds are looking too high for you, it might be time to cancel your summer holiday to the Blue Mountains. You wouldn’t want to risk a lifetime enjoyment of burgers, right?
– Head here to listen to the fantastic Radiolab podcast on this topic from 2016