A growing number of people around the world are being diagnosed with a strange, potentially life-threatening allergy to red meat — caused not by the meat itself, but by tick bites.
The condition, known as alpha-gal syndrome, develops after a person is bitten at least twice by ticks carrying a sugar molecule called alpha-gal in their saliva. The bite triggers immunoglobulin E antibodies, so later exposure to alpha-gal — found in red meat and dairy products — can set off an allergic reaction ranging from stomach pain to life-threatening anaphylaxis. At least two people have died from it worldwide.
Cases are climbing in many countries. Australia has the highest rates on Earth, with more than 700 affected people per 100,000 in some tick-prone regions and suspected cases up 22 percent each year since 2020, mostly from the Australian paralysis tick. In the United States, as many as 450,000 people may have the allergy, according to the CDC, with around 15,000 new diagnoses a year linked mainly to the lone star tick. In Japan, up to 4.9 million people have been exposed to alpha-gal and produced antibodies, while sensitization in Denmark more than doubled between 1990 and 2016.
Researchers point to climate change — which is expanding tick habitats — and growing deer populations as key drivers. Yet much remains unknown: symptoms are vague and can appear hours after eating meat, so the condition is probably under-diagnosed, and there is no treatment or cure.
"We're still casting in the dark, but it is our responsibility to find something that works for people," says Benjamin Casterline, an immunology researcher at the University of Missouri School of Medicine.
