Alpha-gal syndrome: How tick bites are triggering life-threatening meat allergies across the US

A tick bite is usually associated with infections such as Lyme disease, but health officials are warning about another potentially serious consequence: a rare allergy that can make eating meat dangerous. Known as alpha-gal syndrome, the condition is triggered when certain tick bites cause the immune system to react against a sugar molecule found in the meat of mammals.

Once considered a little-known condition, alpha-gal syndrome cases are rising across the United States as more people report allergic reactions after consuming beef, pork, lamb and in some cases, dairy products. Symptoms can range from hives, itching and digestive problems to severe reactions, including breathing difficulties and life-threatening anaphylaxis.

Unlike typical food allergies that appear immediately after eating, alpha-gal syndrome often causes delayed reactions, making it harder to identify. Researchers say the increase in cases is linked not only to greater awareness and diagnosis but also to the expanding range of tick populations, particularly the lone star tick, which is considered the primary source of the condition in the US.

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With an estimated hundreds of thousands of Americans potentially affected, doctors are urging greater awareness about the warning signs, diagnosis and prevention of a condition that can change a person’s diet and daily life after a single tick bite.

How a tick bite causes a meat allergy

Alpha-gal syndrome is not caused by bacteria or viruses like many other tick-borne illnesses. Instead, it develops when certain ticks introduce alpha-gal molecules into the bloodstream through their saliva during a bite.

The immune system then creates antibodies against the molecule, treating it as a harmful foreign substance. Later, when a person consumes mammalian meat containing alpha-gal, the immune system may launch an allergic response.

“Skin is a fantastic way to make an allergic response,” Dr. Scott Commins, an alpha-gal syndrome researcher at the University of North Carolina told AP, explaining why exposure through a tick bite can trigger an allergy that eating meat alone does not.

The condition was first linked to tick bites about 15 years ago, but awareness and reported cases have increased in recent years. Researchers say the rise may be partly due to better recognition among doctors and the public, as well as the expanding range of tick populations.

Growing tick populations fuel concern

The lone star tick, identified by a distinctive white spot on its back, is considered the main source of alpha-gal syndrome in the United States. While it has historically been concentrated in the eastern and southern parts of the country, researchers have reported its presence in new areas, including parts of the Great Lakes region and as far north as Martha’s Vineyard in Massachusetts.

Scientists are also investigating whether other tick species, including blacklegged ticks, may contribute to the spread of the condition.

A 2023 study by the US Centers for Disease Control and Prevention estimated that around 450,000 Americans may have developed alpha-gal syndrome, although experts believe many cases may still go undiagnosed.

People often seek medical attention after experiencing symptoms such as hives, dizziness, breathing problems, swelling of the lips, tongue or throat, or severe digestive issues including stomach pain, vomiting and diarrhoea.

Diagnosis typically involves a blood test that detects alpha-gal antibodies, along with a review of symptoms and possible tick exposure. However, doctors caution that a positive antibody test alone does not always mean a person has the allergy.

Avoidance remains key, but new treatments emerge

The main approach to managing alpha-gal syndrome has been avoiding foods made from mammals, including beef, pork and lamb. Some patients may also need to avoid products containing animal-derived ingredients such as gelatin, which is used in items like marshmallows and gummy candies.

People with severe reactions are advised to carry epinephrine injectors for emergencies.

The condition can also affect medical care, as some products and implants, including certain heart valves, are made from animal tissues.

In some patients, the allergy may gradually disappear over time. Researchers have observed improvement in a portion of patients after several years, but avoiding additional tick bites remains important because new exposure may worsen the condition.

In 2024, the US Food and Drug Administration approved Xolair (omalizumab) for food allergies, including alpha-gal syndrome. The drug does not eliminate the allergy but can reduce the risk of severe reactions following accidental exposure.

Scientists are continuing to explore additional treatments that could interfere with the immune pathways responsible for allergic reactions, raising hope for more effective therapies in the future.

With inputs from agencies