Alpha-gal syndrome (AGS), also known as alpha-gal allergy or mammalian meat allergy (MMA), is an acquired allergy to the epitope of the carbohydrate molecule galactose-alpha-1,3-galactose ("alpha-gal"). Reactions can be life-threatening, and typically either begin rapidly after exposure from intravenous therapy, or 2–8 hours after ingesting foods and medicines. Reactions can also occur from skin contact and environmental exposures. AGS results from tick bites, and possibly bites from other parasites.
Alpha-gal is present in all foods and ingredients made from beef, pork, lamb, venison, rabbit, and other mammal sources, including gelatin and milk. Certain seaweeds also contain alpha-gal. Alpha-gal is found worldwide among the inactive ingredients and materials of medications and healthcare products, and it is generally not required to be labeled. Reactions have been reported from breathing cooking fumes containing alpha-gal molecules, and from contact with health and personal care products. AGS patients may have a reaction near farm animals, and shoveling manure or other chores may require gloves or a respirator.
Signs and symptoms Reactions have been documented from intravenous medication, foods and medicines, skin contact, and environmental exposures.
Allergic symptoms vary greatly between individuals and include rash, hives, nausea or vomiting, difficulty breathing, drop in blood pressure, dizziness, diarrhea, severe stomach pain, anaphylaxis, heart attack, and death.
Reactions to intravenous treatments Reactions to intravenous exposure, such as infusions and transfusions, are typically rapid. The cancer treatment cetuximab, gelatin-based plasma volume expanders, and certain antivenoms are forms of intravenous treatment that have been identified as particularly risky for patients with alpha-gal syndrome.
Reactions to foods and medicines
Reactions to alpha-gal in food or medicine typically have a delayed onset, beginning 2–8 hours after consumption. After the delayed onset, the allergic response is like most IgE-mediated food allergies, including severe whole-body itching, hives, angioedema, gastrointestinal upset, and possible anaphylaxis. Anaphylactic reactions are seen in approximately 60% of afflicted individuals.
Some cases feature gastrointestinal (GI) symptoms without pruritus, hives, or other skin involvement. This presentation is not typical of food allergies, which can make the initial suspicion of alpha-gal syndrome less likely. It can lead to misdiagnosis of irritable bowel syndrome. American guidelines published in 2023 recommended physicians suspect alpha-gal syndrome in cases with abdominal pain and GI symptoms, but without traditional allergy symptoms like hives. In 70% of cases, the reaction is accompanied by respiratory distress and is particularly harmful to those with asthma.
The severity of reaction to alpha-gal has been found to correlate with the amount of alpha-gal in the ingested food or drug. However, for many patients, not every exposure to alpha-gal results in an allergic reaction. Symptoms and sensitivity to reactions vary greatly among individuals. Other factors, including exercise and alcohol consumption, can affect an individual's symptoms and reactivity to alpha-gal.
Prevalence Alpha-gal allergy has been reported in 30 countries on all six continents where humans are bitten by ticks, particularly the United States and Australia. Prevalence can be correlated to populations of tick species that have been documented as carriers, such as the lone star tick (Amblyomma americanum) in the US and the paralysis tick (Ixodes holocyclus) in Australia. Alpha-gal has also been shown to exist in the saliva of Ixodes scapularis but not Amblyomma maculatum.
Availability of prevalence data In the United States, data on AGS prevalence is limited because positive blood test results and clinical diagnoses are not required to be reported in federal public health statistics. AGS is only a mandatory reportable condition for statistics in some US states. In September 2023, Arkansas became the first US state to make alpha-gal syndrome a reportable condition. As of June 2026, thirteen states track positive tests.
Australia In November 2019, Australia had the highest rate of alpha-gal syndrome and tick paralysis worldwide.
United States From 2010 to the end of 2022, over 100,000 cases of AGS were diagnosed by a laboratory in the United States. The Centers for Disease Control and Prevention's national estimate of cases totaled 450,000 at that time. The CDC report indicated that those numbers were likely an underestimate because AGS is neither nationally "reportable" nor mandated as reportable in all states, and also because many medical providers remain unfamiliar with AGS.
In a 2010–2018 study, more than 34,000 suspected cases of AGS were identified. After that period, the annual number of positive test results increased from 13,371 in 2017 to 18,885 in 2021. Virginia reported 14,000 positive cases from September 2025 to June 2026, ten times its rate of Lyme disease.
In the US, AGS is more prevalent in the central and southern regions, which corresponds to the distribution of the lone star tick. In the Southern United States, where the tick is most prevalent, allergy rates are 32% higher than elsewhere. 2012 research identified unexpectedly high rates of alpha-gal syndrome in certain western and north-central areas of the US. This suggests that another tick species may spread the allergy. The study also found alpha-gal syndrome cases in Hawaii, where no ticks associated with AGS are found.
Prognosis Alpha-gal syndrome is a long-term condition for which there is no cure. AGS can be fatal. AGS disproportionately affects people in their 40s and 50s when the human body begins to lose cardiac resilience. 30–40% of AGS patients have cardiac symptoms during reactions.
Management typically requires ongoing access to a medical provider and avoidance of the alpha-gal molecule epitope. Symptoms may lessen or resolve over time for some AGS patients. For some people, the allergy improves after avoiding further tick bites over a time period from 8 months to 5 years.
Treatment In addition to avoiding triggers, treatment aims to alleviate symptoms and is dependent on severity. If an individual with mild symptoms consumes food containing alpha-gal, then treatment with over-the-counter antihistamines may be acceptable. More severe reactions—like anaphylaxis—can require admission to a hospital for emergency treatment. In these situations, treatment is the same as for any anaphylactic reaction, such as epinephrine administration.
Desensitization Desensitization involves the gradual introduction of increasing amounts of mammalian meat under medical supervision. The process is experimental and requires extended monitoring due to the risk of delayed anaphylaxis.
Successful oral desensitization for alpha-gal syndrome has been reported in multiple cases including two adults in 2017, a pediatric case in 2019, an adult in 2023, and a 63-year-old in 2024.
Deaths More than 10 deaths have been attributed to alpha-gal reactions to medications.
Availability of mortality data There is no estimate of the number or rate of deaths due to alpha-gal syndrome. Awareness among healthcare providers remains limited, and AGS often goes undiagnosed, leading to AGS deaths not being reflected in public health data. Patients with life-threatening AGS symptoms often remain undiagnosed even after emergency department visits. One study in North Carolina evaluated more than 100 medical encounters with AGS patients, including 28 emergency department visits and 2 urgent care visits. The correct AGS diagnosis or an effective diagnosis referral occurred less than 10% of the time.
Reactions to intravenous treatments In 2006, a patient in the United States died from an anaphylactic reaction following an infusion of cetuximab.
In 2010-12, a paper proposed that approximately 8 deaths could be attributed to anaphylactic reactions to cetuximab across Italy and France, with one additional death being reported but unpublished in the medical data. "Environmental factors, such as bites by ectoparasitic ticks, probably explain the heterogeneous ... incidence of anaphylactic reactions to cetuximab among studies and geographic areas."
In 2021, a forensic investigation confirmed that a fatal reaction to cetuximab in South Korea was due to alpha-gal syndrome.
A review from Australia connected anaphylactic reactions as a result of cetuximab administration to alpha-gal syndrome, noting that there had been two fatal cases before July 2022. In 2023, AGS experts Sheryl van Nunen and Melanie Burk reported that 3 deaths from cetuximab-triggered AGS reactions had occurred in Australia that year, and 8 in the rest of the world, totaling 11 deaths.
An case report from Washington DC documented three alpha-gal reactions in 2022 and 2023 to type B blood transfused to a type O patient, including one death from Transfusion Related Alpha-Gal-Syndrome (TRAGS). AGS may have caused the death of a Kansas woman in 2025 after heart surgery.
Reactions to food ingredients The earliest known forensically documented fatal case of AGS from consuming mammal food products occurred in Australia in 2022. In November 2025, researchers at the University of Virginia School of Medicine described another fatal allergic reaction due to undiagnosed alpha-gal syndrome that occurred the previous summer. The cause was determined post-mortem because the deceased's family requested an investigation. AGS may have caused the reaction that killed a person in the United States in 2023 from an anaphylactic reaction to beef. One expert noted in 2025 that there were additional unreported deaths from food reactions.
Sources of alpha-gal epitope Galactose-alpha-1,3-galactose, or alpha-gal, is a carbohydrate molecule found widely in natural and manufactured substances.
Foods
Alpha-gal is a natural component of food ingredients made from mammals such as beef, pork, lamb, venison, rabbit, gelatin, and milk. Individuals with an alpha-gal allergy may still consume reptile meats, insects, poultry, and seafood that naturally do not contain alpha-gal.
The alpha-gal molecule can also be found in certain seaweeds. Carrageenan is the name for a group of linear sulfated polysaccharides that are extracted from red algae, or red seaweed. Carrageenan contains the alpha-gal epitope that some people with alpha-gal syndrome react to. Carrageenan is used for gelling, thickening, and stabilizing, as well as for clarifying beer, juice, and wine. Carrageenan is also sprayed on fruit and vegetables, and applied to fish to help them retain water. It can also be found in medications, medical products, personal care, and household products.
Some alpha-gal reactions attributed to dairy may instead be to carrageenan. Common names for carrageenan include: PES Irish Moss, Vegetable Gelatin, Norsk Gelatin, Danish Agar, Carastay, Eucheuma spinosum gum, and red seaweed extract.
Medication and medical products