Allergies can be life-threatening health issues, and now doctors are seeing a relatively new one: an allergy to meat. Patients have reported rashes, hives, even anaphylactic shock hours after eating a steak or hamburger. This allergy can be dangerous; anaphylactic shock can be fatal, and the incidence of the allergy seems to be on the rise.
The cause is a sugar known as alpha-gal, present in beef and pork (as well as the meat of all other mammals that are not primates).
The allergy that develops to that sugar starts with a tick bite, which took researchers some time to figure out. One factor adding to the confusion was the relatively long time it took for the reaction to appear, which was several hours after a person ate meat. Normally, food allergies produce reactions in an hour or less. The delay is, in part, because alpha-gal tends to be concentrated in fat, and fat moves through the digestive system slowly.
An associate professor of medicine at the University of Sydney Medical School, Sheryl van Nunen, got credit for first making the connection between tick bites and meat after she started seeing unusual numbers of cases of anaphylaxis. While the condition is rare, van Nunen says that it’s the most common cause of anaphylaxis in Sydney.
The culprit there is the paralysis tick. Where alpha-gal allergies have appeared in Europe, they’ve been blamed on the castor bean tick. In the United States, the lone-star tick, whose territory covers most of the eastern half of the country, has been implicated. The tick, whichever kind it is, needs only to bite its host. It doesn’t need to stay attached for long. During the bite, alpha-gal is injected into the skin. In some people, this causes the immune system to release a flood of antibodies, which then signal the body to release histamines to fight off the perceived allergen. The body is now sensitized to alpha-gal. When the person next eats meat, alpha-gal is introduced to the body again and the reaction, the overreaction, begins. The body detects a threat and deploys the antibodies.
Researchers investigating the alpha-gal allergy have now also documented the first U.S. cases of another rare meat reaction: pork-cat syndrome, which is an allergy to pork caused by a sensitization to cats. It’s been known in Europe since the 1990s.
The researchers found that some people, almost all of them cat owners, develop an allergic response to a protein made by a cat’s liver that cross-reacts with albumin in pork. When these people ate pork, they had severe allergic reactions, including hives and anaphylaxis.
Experts describe meat allergies as being quite rare, at least in terms of documented cases. They suspect there are many more cases still undiagnosed. The only way to a definitive diagnosis is a blood test, and the only cure is giving up red meat. But an alpha-gal allergy does seem to go away in time, though it may take several years.