It’s an unusual condition that has only been recognized for less than a decade: red meat allergy. The allergy develops after a bite from a Lone Star tick triggers a person’s immune system to begin producing IgE antibodies to alpha-gal, a sugar found in meat such as beef, lamb, venison and pork.
It can be a confounding condition to diagnose. Unlike other food allergies in which a reaction occurs soon after eating – alpha-gal meat reactions often don’t develop until three to six hours after red meat has been consumed. So while the allergic symptoms (ranging from hives and itchiness to full-blown anaphylaxis) may be obvious, doctors and patients can miss that red meat is the culprit.
Researchers at the University of Virginia first published a paper on alpha-gal allergy in 2009, and then confirmed the association with tick bites in 2011. One of the experts involved in this research is Dr. Scott Commins, an allergist who’s now an associate professor of medicine at the University of North Carolina. Allergic Living recently spoke to the expert – to find out the latest on the allergy that takes red meat off the menu.
Is the incidence of red meat allergy rising?
“I think it really is increasing,” says Commins. He says there are 3,500 documented reports of red meat allergy in the United States, and suggests the number is even higher. While the recent availability of blood testing for alpha-gal allergy may have improved diagnosis, it also seems a true increase.
“When we put out that first paper in 2009, we had 24 patients and we had to get five of those from southern Missouri,” says Commins. When he speaks to fellow allergists, this allergy “has really has taken over the adult food allergy side in a lot of the southeastern and eastern U.S. states practices.”
The habitat of the Lone Star tick (Amblyomma americanum) also appears to be expanding. While reports of red-meat allergy were originally confined to Virginia, North Carolina, Tennessee, Arkansas and Missouri, some cases are now reported in states like Ohio and New Jersey. One allergist based on Long Island, New York says she has over 200 patients with red meat allergy – patients who got tick bites.
Does the tick bite allergy issue arise in other countries?
The Lone Star tick is not so “lone” as an allergy-triggering arachnid. Commins says red meat allergy has “gone global” in countries that don’t have Amblyomma americanum ticks but do have other tick species.
“The Australians are having big trouble with this; France, Germany, and southern Sweden are having issues. The global data indicate that this is a wider issue than just Lone Star ticks.”
If you know you’ve had a tick bite, should you be tested for alpha-gal allergy?
Not without symptoms, says Commins, reminding that “there are plenty of people who get tick bites and do not end up with this allergy. But I ask patients to be aware of the site of the tick bite. If it gets really red, itchy and swollen and hangs around for 14 days, I then ask them to keep an eye on any unusual symptoms like itching and hives, or gastrointestinal distress.”
With this allergy, does the type of meat that was eaten affect the level of reaction?
“Yes, we’ve seen that the fattier the meat, the more likely and the more severe the reactions,” says Commins. “We think that fat is where the actions is, which explains the delayed response – because fat is absorbed very differently.
So a hamburger might put you at greater risk of a severe reaction than beef tenderloin? “That seems to be true,” says the expert.
If you have an allergy to beef, will you also react to cow’s milk?
Commins says some people with the allergy are affected by cow’s milk and dairy, including ice cream – but it’s not everyone. “There certainly are some folks with this allergy who really have trouble handling dairy.”
If you have this allergy, you are supposed to avoid all red meat. Should you also carry epinephrine?
Yes, says Commins, since symptoms can range up to anaphylaxis. “I do ask my patients to carry epinephrine.”
Dogs are certainly “outdoorsy” and often get tick bites. Can a dog also get this red meat allergy?
“We have a little bit of preliminary data to indicate that this may actually be an issue,” says Commins. In fact, he is planning to study this, and has already been speaking to veterinarians in the Chapel Hill, NC area.
“Apparently beef is one of the foods that dogs can become fairly allergic to. And certainly they have tick bites [in this area], so this could perhaps be part of that process.” However, they won’t know for certain whether it’s alpha-gal allergy until this is studied.
How does alpha-gal exposure from the tick happen?
Commins says this is still under study. “We’re actively working on it and we don’t know. We don’t understand why some tick bites do this – and others don’t. And it could be that it’s the host, that it’s the person. Or it could be that the tick has to have fed on a deer or a dog and then bites the human. We don’t yet know if it’s really specific for certain ticks based on their feeding.”
What is the therapy that’s being developed to treat red meat allergy?
Commins explains that his team is working to develop a form of allergy shots, similar to how stinging insect allergies are treated with venom immunotherapy.
First the team has to identify the antigen that causes the allergic response. “We think it’s in the salivary glands, so it may be that we can use purified ticks salivary glands to treat.”
There is also this good and bad news on the lifespan of this allergy: “We think this goes away over time naturally,” he says. “The problem is that additional tick bites will cause it to hang around or even recur.”
A parting question: Is tick bite the only example of another species abetting a food reaction?
Apparently again, the Lone Star tick is not so lone. Commins cites a fascinating example: “There’s a report from Japan of surfers who are getting bites from jellyfish and then becoming allergic to a traditional food (fermented soybeans or natto).”
“The whole point,” he says, “is this idea of something happening to the skin and creating an allergic response that then is triggered by food intake.”
See also: CDC’s tick bite prevention tips