What is Alpha-Gal
After the second bout of a horrible allergic reaction, I began to seriously consider the possibilities. The first incident I thought was a reaction to legumes – I had eaten a handful of peanuts only 10 minutes prior to the symptoms. I had heard of the sudden onset of legume allergies in adults. But, after the second incident I seriously began to consider the possibility that I had this new “red-meat allergy”. Upon reflection, both times I had eaten red meat (any mammal meat). This may seem a desperate correlation, but I had severely cut back on my meat intake. In fact, the two times, months apart, I could remember eating red meat during this period, I had these reactions. Furthermore, the reactions occurred several hours after eating red meat – a phenomenon of this allergy.
First documented in 2009, alpha-gal induced allergic reactions were reported in 24 cases (Commins and Platts-Mills, 2009 and 2013). Commins and Platts-Mills papers include a lot of medical jargon, descriptions of other closely related allergies, and explanations of experiments and assays performed in the study of this relatively new allergy. I will spare you those details and attempt to distill the most important points.
Alpha-gal, or galactose-alpha-1, 3-galactose is a carbohydrate, which is, in biochemistry, is a group of compounds that includes sugar. Organic sugars of several varieties are found in fruits, vegetables, and other foods. Alpha-gal, is a common component of the cell membranes of many mammal species, excluding old world primates and humans. So, if you are reading this, you do not have naturally occurring alpha-gal coating your cell membranes like a sugar dipped lollypop. Under certain circumstances, outlined below, alpha-gal can cause the body’s immune system to develop a novel antibody, IgE. Antibodies are what your body produces to defend from outside pathogens (i.e. bacteria, viruses , etc…) The overproduction of antibodies in response to certain stimuli is what often causes various forms of allergies. The alpha-gal allergic condition – delayed anaphylaxis to mammalian meat – requires the development of the IgE antibody.
As best as scientists who study this can tell, it starts with ticks and land mammals. In the United States, the culprit is the lone star tick (Amblyomma americanum), common throughout the eastern US. As an ectoparasite, these ticks make their living sucking blood from hosts. These hosts may include all kinds of animals such as lizards and birds; however, frequently their host is a mammal including rodents, deer, dogs, cats, and humans! We’ve all had experiences with ticks if we’ve spent any substantial amount of time romping around in the forest.
Once a tick has found a suitable host, they can remain attached for up to a week. The lone star tick is a generalist feeder, taking advantage of any number of hosts. Also, they require at least three hosts to complete their life cycle from larvae to nymph to adult. During this period, these ticks likely will take up residency in various mammalian species. Now we get back to alpha-gal; during this period ticks are likely to ingest a fair amount of mammalian blood and, guess what, the carbohydrate alpha-gal along with! Once a tick gets to a point of host switching, they already have this carbohydrate in their bloated gut. The tick then searches out a new host to become an adult, produce more little baby ticks, and complete its life cycle. If you find yourself ambling in the woods, in the right part of the country, you are very likely to find yourself eventually playing host to one or more of these little blood suckers.
Once you are ‘bitten’ by a tick, the process begins. We’ve all used straws before and know how easy it is to reverse flow, even for a split second, and eject some of our own saliva in the drink. Well, imagine ticks doing a bit of the same. Except, they may actually eject a little more than just saliva. Having blood, and quite possibly, alpha-gal in their guts from previous hosts, they can purge a little of that into your own blood stream when attached. What happens then?
To answer that question, let’s back up a bit. Remember, alpha-gal is found in all non-primate mammals (i.e. cows, pigs, deer ,etc…). So, we have all ingested alpha-gal containing foods in our lifetimes – providing we have eaten mammal meat at some point. So why aren’t we always breaking out in horrible allergic reactions? Well, it has to do with our body’s immune system.
In a non-afflicted individual, alpha-gal containing food is broken down through various processes in the digestive system. Eventually, the alpha-gal itself may even be released through the intestinal walls. However, your body breaks all this down, harvests energy from the meal, excretes excess waste, and you happily go on your merry way.
Now back to the tick bite. Once the tick has bitten and, if, it releases contents including alpha-gal in your blood stream, your body sets of an immune response to fight against this foreign substance. Inflammation, irritation, and itching are all common symptoms. This is actually what happens most times we are bitten, stung, or poked by a plant or animal. Think of a mosquito bite. However, in this particular case, our body may develop an immune response to the foreign substance, alpha-gal. Think of your immune system as having a memory. Our body has now seen this foreign substance from an external wound; it now has learned to respond to it whenever it is found.
As an afflicted individual eats a burger, or steak, or anything with mammal meat, the alpha-gal released during digestion into the blood stream sets off a systemic (whole body) allergic reaction. I had hives from my head to my feet. Of the many peculiarities, the allergic reaction may take 3-6 hours to set it (Commins and Platts-Mills 2013). This was one reason why early in the history of the condition, many doctors dismissed patients concerns that they may have a food allergy to meat. Food allergies commonly only take minutes to set in, not several hours. And, while the cause of this allergy is becoming better understood, little is known about some of the details. Why the delayed allergic response? Can the allergy wear off given enough time? How many people does this allergy afflict?
Commins and Platts-Mills report that many patients develop allergic response to ingested mammalian meat 3-6 hours after eating, and that the role of lipids in the food may produce this pattern (2013). Alpha-gal containing lipids in the meat are not immediately released upon eating, and can take several hours to be absorbed. Other interesting patterns deal with the timing and severity of the allergic reactions. The study found that some patients could tolerate small amounts of meat (e.g. a single strip of bacon) with no response. Large amounts of meat (e.g. double burger) could cause severe reaction and even affect several organ systems (Commins and Platts-Mills 2013).
Furthermore, the timing and severity of tick bites may influence the severity of the allergy. Patients with recent and higher doses of tick bites (i.e. more bites, more reaction to bites) were more likely to develop delayed allergic response to mammalian meat (Commins and Platts-Mills 2013). This provides evidence for the possibility that the allergy may wear off over time; providing you stop getting bitten by ticks, and thereby exposed to further alpha-gal. However, much is still unknown and proper diagnosis and caution should be used.
Finally, how many people may have this condition? This is a hard number to come by. It was first described in 2009 from 24 cases (Commins and Platts-Mills 2009; 2013); however by 2012 it was evident that the total number of cases was likely in the thousands. Furthermore, because the condition has only recently been described, it is likely that many cases when undiagnosed over that last several decades. The true number may forever evade us. Further complicating the matter is that the severity of reactions differs among many people; some people may never develop strong allergic responses. Others, perhaps vegetarian, pescatarian, or who don’t eat any mammal meat, may never discover they have the condition.
As the condition becomes better understood, it may become more easily diagnosed. My doctor ordered the correct allergy tests, and with a small vial of blood, was able to diagnose the condition. In popular culture it has even received recent attention. The October 27, 2016 episode of Radiolab covered the story of Amy Pearl who developed alpha-gal allergies. I highly recommend the episode as it is both educational and humorous!
Why I Don’t Eat Mammals Part 1: http://wp.me/p4iZnM-4m
Commins SP., and T.A. Platts-Mills. 2009. Anaphylaxis syndromes related to a new mammalian cross-reactive carbohydrate determinant. J Allergy Clin Immunol. 124(4): 652-657.
Commins SP., and T.A. Platts-Mills. 2013. Delayed Anaphylaxis to Red Meat in Patients with IgE Specific for Galactos alpha-1,3-Galactose (alpha-gal). Curr Allergy Asthma Rep. 13(1): 72-77.