Some unfortunate people suffer from severe recurrent allergic reactions in which their airways close up and their blood pressure crashes to dangerous levels – and yet they are none the wiser to their cause. Well a new study published in the journal Allergy found that in the United States, up to almost 10 percent of these unexplained anaphylaxis cases may be down to tick-induced meat allergies.
This may sound like something from science fiction, but in recent years there's been a growing awareness to the reaction caused by a rare arachnid known officially as the lone star tick, but also as the “reverse zombie” tick. When some people are bitten by this little beastie, it can cause them to become allergic to red meat, and it might be more common than thought.
For the study, the team examined unexplained anaphylaxis in 70 patients and found that six of them tested positive for being allergic to galactose-a-1,3-galactose (alpha-gal). This is a sugar that is only found in non-primate mammals and is a prime indicator they've been bitten by the lone star tick. This means that up until now, their unexplained allergic reaction is due to red meat.
It is thought that when the ticks bite a human after having fed on another mammal, the sugar found in these wild animals' blood gets mixed in with the ticks’ saliva and injected into the body. As the immune system launches its attack against the tick, there is a crossover and the body not only produces antibodies against the arachnid, but also against the sugar alpha-gal.
This means that whenever the body then experiences the sugar again, such as after eating meat, the body launches another attack and causes the allergic reaction.
“We often think of ticks as carriers of infectious diseases, such as Lyme disease, but the research strongly suggests that bites from this particular species of tick can lead to this unusual allergy,” says co-author Melody C. Carter, staff clinician at NIAID’s Division of Intramural Research, in a statement. “The association is increasingly clear, but we still need to discover exactly how these two events are linked and why some people with similar exposure to tick bites seem to be more prone to developing alpha-gal allergy than others.”
They found that the six people suffering from the allergy did indeed have a history of being bitten by juvenile lone star ticks. The natural distribution of the ticks in the southwest of the United States, as well as New York, New Jersey, and New England, matches well with the reported cases of the allergy.
It's possible that the gap between eating the meat and the reaction, which is typically three hours, slows diagnoses of the allergy.