EASTERN AND SOUTHERN U.S. — The FDA approved the injectable medication Xolair in 2024 for alpha-gal syndrome and other food allergies. Alpha-gal syndrome is a meat allergy caused by tick bites, affecting an estimated 450,000 Americans, according to a 2023 study by the Centers for Disease Control and Prevention.

The syndrome results from an immune response to a sugar known as alpha-gal. Tick bites introduce this sugar into the bloodstream, triggering specific antibodies. Alpha-gal is present in most mammalian meat and tick saliva, absent in humans and primates. Dr. Scott Commins, a University of North Carolina researcher, said, "It turns out that the skin is a fantastic way to make an allergic response. If this all happened orally, and we were eating alpha-gal like we do with steaks or barbecue, then we wouldn't become allergic."

The primary source in the U.S. is the lone star tick, identifiable by a white dot on its back. This species is most common in the eastern and southern U.S. In recent years, lone star ticks have also been documented in the Great Lakes region and in Martha's Vineyard, Massachusetts.

Symptoms typically include hives, diarrhea, and itchiness, appearing hours after consuming meat or dairy. Other symptoms include dizziness, difficulty breathing, and swelling of the lips, throat, tongue, or eyelids. Some patients experience only digestive issues like stomach pain, vomiting, and nausea. The allergy does not affect seafood, poultry, chicken, turkey, or eggs.

Diagnosis relies on blood test results, symptoms, and patient-reported details about recent insect bites. Commins said, "The blood test in and of itself is great, but you can't rely on that just for diagnosis. You need the actual symptoms too. In the allergy world, we have a lot of trouble with false positives on blood tests." Guidance involves avoiding beef, pork, lamb, and other mammalian meats while carrying an epinephrine injector. Some patients can consume dairy, while those with severe reactions may need to avoid animal byproducts like gelatin.

Xolair reduces reaction severity after accidental meat consumption, but does not cure the condition. It functions by decreasing release of compounds that trigger inflammation and allergic responses. It was initially approved over two decades ago for patients with severe asthma. Maria Diuk-Wasser, a Columbia University researcher, said, "I think part of it is more people have learned about it and are on the watch for this syndrome." The allergy resolves in some after several years; Commins documented resolution in 15% to 20% of patients. He said, "There are certain biologic drugs out there nowadays that interfere with the allergic signaling. We think that if you were on one of those or if you got one quickly enough after a tick bite, perhaps it could interfere with the entire allergic response process."