Alpha-Gal Syndrome: a rising food allergy in the US linked to tick bites

Alpha-Gal Syndrome (AGS), a novel food allergy to meat induced by tick bites, is believed to be more widespread in the US than previously estimated. The US Centers for Disease Control and Prevention (CDC) now suggests that as many as 450 000 Americans could be affected by this emergent allergy.    

The term AGS is derived from a carbohydrate molecule, galactose-1,3-galactose, or alpha-gal, found in most mammals' proteins, excluding primates. Alpha-gal is present in various mammal tissues and animal products, including pork, beef, rabbit, lamb, milk, and gelatin. Interestingly, alpha-gal is also found in tick saliva, which has led to an unexpected allergic reaction in some tick bite victims.    

After a tick bite, certain individuals develop an antibody known as anti-alpha-gal IgE, which not only defends against future tick bites but also triggers an allergic reaction to any alpha-gal-containing substance, such as meat and animal products.    

According to a study published on July 28, which investigated AGS prevalence and distribution in the US, it is critical to raise awareness about this condition. The study analyzed alpha-gal-specific IgE antibody (sIgE) test results from 2017 to 2022, covering over 295 000 individuals nationwide. Approximately 30.5% (90 018 individuals) tested positive, indicating likely AGS. Although the positive rate remained relatively consistent at 30%, the total number of tests increased annually, leading to a surge in suspected new AGS cases—an estimated 15 000 each year.  
Combining the 90 018 suspected cases from 2017 to 2022 with the cases from 2010 to 2018, researchers concluded that there were 110 229 suspected AGS cases from 2010 to 2022.    

Common AGS symptoms include hives or itchy rash, nausea or vomiting, heartburn, diarrhea, cough, shortness of breath, a drop in blood pressure, swelling of the lips, throat, tongue, or eyelids, dizziness or fainting, and severe stomach pain.  
Uniquely, AGS symptoms typically manifest two to six hours post-consumption of alpha-gal-containing food or exposure to other types of carbohydrates, such as those in gelatin-coated drugs. This delayed reaction distinguishes AGS from more common allergies, which usually produce symptoms within minutes of allergen ingestion.  
The severity of AGS reactions varies among individuals, ranging from mild to potentially life-threatening scenarios like anaphylaxis, warranting immediate medical attention.  

 "AGS is a significant emerging public health issue with potentially severe, lifelong health implications for some patients. Clinicians must be aware of AGS to properly evaluate, diagnose, manage, and educate their patients about tick bite prevention, crucial for averting AGS," a statement from the CDC emphasized.