Alpha Gal Red Meat Allergy

(March 3, 2019); updated January 1, 2021

New research suggests that odds are even greater that a tick bite can trigger allergies to hamburgers, steak, pork, and other red meat

A paper presented at the February 2019 American Academy of Allergy, Asthma and Immunology (AAAAI) annual conference in San Francisco sheds new light on a strange food allergy that is brought on by a tick bite. "Alpha gal" is a sugar found in the blood of most mammals, but not in humans or other primates. Since the mid-2000s, it has been known that Lone Star tick bites can trigger an allergic immune response in humans to this sugar. The assumption has been that ticks needed to feed on a non-primate mammal before biting a human to trigger the allergic response in humans. But a recent University of North Carolina study, led by Dr. Scott Commins, suggests that tick bites may trigger the "alpha gal" meat allergy through their saliva even if they have not recently fed on a mammal. Researchers suggest that the allergy trigger could be inherent in the saliva of the tick itself, not in the mammal's blood that they consume. This means that the potential tick population capable of transmitting the allergen is much greater than was thought previously, making more people at risk.

Unlike other food allergies, which appear within minutes of eating, the allergic reaction triggered by eating beef or pork will not occur until three to six hours after eating.This has sometimes made it a difficult condition to diagnose, although doctors are becoming more aware of this unusual allergy. Ticks most likely to transmit the allergy tend to live in the southeast region of the United States and certain areas of New York, New Jersey and New England. Still fairly rare, the condition affects more people each year, with at least 5,000 cases documented in the southeast. For now, treatment for "alpha gal syndrome" is simple: not eating beef or pork. Patients must avoid eating all red meat, and some patients must also avoid eating gelatin or taking animal-derived biological drugs such as the cancer drug called cetuximab. Research has suggested that some gelatin-containing vaccines, such as the zoster (shingles) vaccine, can also trigger serious allergic reactions in patients with alpha gal syndrome.

Rocky mountain tick
Lone Star tick

Trivia question:

Is the tick the only animal that can trigger an allergy to a food?

"Apparently again, the Lone Star tick is not so lone. Commins cites a fascinating example: There's a report from Japan of surfers who are getting bites from jellyfish and then becoming allergic to a traditional food (fermented soybeans or natto)." (from Allergic Living, cited below)

Update: December, 2020: U.S. Food and Drug Administration approved a first-of-its-kind intentional genomic alteration (IGA) in a line of domestic pigs, referred to as GalSafe pigs, which may be used for food or human therapeutics. This is the first IGA in an animal that the FDA has approved for both human food consumption and as a source for potential therapeutic uses. The IGA in Revivicor Inc.'s GalSafe pigs is intended to eliminate alpha-gal sugar on the surface of the pigs’ cells.

Sources and More Reading

Press release:

"Red Meat Allergy: Incidence on Rise, Therapy in Works" (Question and answer with Dr. Scott Commins):

From the Journal of Allergy and Clinical Immunology, Programs and Abstracts of Papers to be Presented During Scientific Sessions: 2019 AAAAI Annual Meeting on Saturday, February 23, 2019: Red Meat Allergy May Develop Independent of Tick Blood Meal Status

Another paper presented at the conference presented a theory about why there are few cases of alpha gal in Texas and the gulf coast. A consistent "shortage" of cases of the alpha-gal syndrome (AS) on the Gulf coast: possible relevance of fire ants as a predator of lone star ticks:

Anaphylaxis after zoster vaccine: Implicating alpha-gal allergy as a possible mechanism (May 2017)

National Institute of Allergy and Infectious Diseases (NIAID) article on allergy to a sugar in red meat. In the U.S., juvenile Lone Star ticks, sometimes called seed ticks, are blamed for transmitting the majority of alpha gal allergies. In other countries, however, where the condition has also been documented, other kinds of ticks are responsible. h

FDA press release on approal of genetically altered domestic pig, GalSafe pigs,  intended to eliminate alpha-gal sugar on the surface of the pigs’ cells: