Alpha-gal syndrome (AGS), a potentially life-threatening allergy to red meat caused by tick bites, is spreading further across the United States than previously believed. While scientists long thought only the lone star tick was responsible for transmitting the allergy, new evidence confirms that other tick species—including blacklegged ticks—can also trigger the condition. This discovery suggests that hundreds of thousands of Americans may be at risk in regions previously considered safe from the syndrome.
For years, the lone star tick, primarily found in the Eastern, Southeastern, and South-Central U.S., was considered the sole culprit behind AGS. However, recent studies from the Centers for Disease Control and Prevention (CDC) have identified cases where bites from blacklegged ticks—commonly known as deer ticks—led to the same allergic reaction. Estimates indicate that between 2010 and 2022, as many as 450,000 Americans may have developed the condition.
Dr. Bobbi Pritt, a pathologist and microbiologist at the Mayo Clinic, explains that this new understanding broadens the geographic risk of AGS. “These findings mean that healthcare providers in states like Maine and Oregon, where lone star ticks are rare, need to be aware of AGS symptoms,” she said.
How Alpha-Gal Syndrome Develops
AGS occurs when a tick bite introduces alpha-gal, a carbohydrate found in non-primate mammals, into a person’s bloodstream. The immune system responds by producing IgE antibodies, which later react when the person consumes red meat or dairy. This delayed reaction—often occurring hours after eating—can cause symptoms ranging from hives and stomach pain to life-threatening anaphylaxis.
While some patients see their IgE levels decrease over time, allowing them to safely eat meat again, subsequent tick bites can reactivate the allergy. This makes prevention crucial, especially as tick populations expand into new areas.
Cases Highlight the Expanding Threat
Two CDC case studies illustrate how blacklegged ticks are now linked to AGS. In Oregon, a 61-year-old woman suffered severe allergic reactions—including throat swelling and wheezing—after eating beef and pork. Testing confirmed AGS, and further tick bites worsened her condition. Similarly, a Maine woman developed gastrointestinal distress after consuming red meat following a deer tick bite. Over a year, her allergy subsided, but the case proved that blacklegged ticks could trigger the syndrome.
A Growing Public Health Concern
Traditionally, AGS was most common in states like Missouri, Arkansas, and Virginia. But the involvement of blacklegged ticks—found along the Pacific Coast, Northeast, and Upper Midwest—means the allergy could emerge in unexpected places. “The geographic range of ticks carrying alpha-gal is more widespread than we realized,” said Dr. Ryan Steele, an immunologist at Yale Medicine.
How to Stay Protected
Since tick bites remain the primary cause of AGS, experts urge vigilance. Using EPA-approved insect repellents, wearing treated clothing, and conducting thorough tick checks after outdoor activities are essential precautions. Pets should also be inspected, as they can carry ticks indoors.
Dr. Johanna Salzer, a CDC epidemiologist, emphasized that while lone star ticks still cause most U.S. cases, other species may play a role. “This is a wake-up call for healthcare providers nationwide,” she said.
As research continues, one thing is clear: AGS is no longer confined to the South. With tick populations expanding, public awareness and preventive measures are more important than ever.
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