how does a tick bite make you allergic to red meat?

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how does a tick bite make you allergic to red meat?

In: Biology

I’m pretty sure the disease is called “Alpha-gal syndrome”. The tick will just burry itself into you and inject you with the sugar molecule called “Alpha-gal”, and could give you the allergy, just like a deer tick carrying lyme’s disease will bite you and inject you with it.

I’m not an expert on this, but I did some reading out of curiosity since I’ve also heard of this phenomenon but didn’t know the details; [this paper](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3545071/) is the main source I used. The allergic reaction you’re asking about occurs in response to a specific carbohydrate known as “alpha-gal”. If you want the technical details, it’s a disaccharide of galactose that looks like [this](https://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Galactose-alpha-1%2C3-galactose.svg/800px-Galactose-alpha-1%2C3-galactose.svg.png). Alpha-gal occurs naturally in most mammals, but for whatever reason the gene which produces it has been lost in some primates, including humans. Since ticks feed on all kinds of animals, they can introduce this chemical to you when they bite you after biting something else first. Because it is not naturally occurring in humans, this chemical is recognized as foreign by the immune system if it is found in your blood, and triggers the production of antibodies in an immune response. As a side note, this same chemical is also apparently one of the major barriers to organ transplants from non-human animals such as pigs; [this paper](https://www.ncbi.nlm.nih.gov/pubmed/10910270) looks into a possible solution to this by modifying pigs so they produce much less alpha-gal.

Just like what happens after you receive a vaccine or beat an illness, your body remembers its exposure to alpha-gal and will keep producing these antibodies for a long time. I’m not totally clear on why this becomes an issue when eating red meat only *after* exposure, but I expect that it has something to do with a greatly increased sensitivity to alpha-gal. Before you got bitten by a tick, you would probably just digest the relatively small amount of alpha-gal you ingested. But after your body finds alpha-gal in your blood, the antibodies it produces make your immune system more “vigilant”, and it will start actively searching for any trace of alpha-gal, which is why you now develop a reaction after eating red meat. An actual immunologist could probably explain this part better.

So to summarize, when ticks bite you they sometimes inject you with a small amount of blood from their previous victims. If these include non-primate mammals (which could be wildlife, livestock, or pets), then they can pass on alpha-gal, which your body then recognizes as foreign material in your blood. This causes an immune response, and has the potential to make you permanently sensitive to this chemical when you ingest it in the form of meat from other mammals. Since birds and fish do not produce alpha-gal, you can still eat them with no problems. Actually, you’d also have no issues if you just switched to cannibalism, so that’s another option!