Meat Allergy: A New Epidemic


 Just when you thought it was safe to wander through the woods, along comes a new observation: the saliva of tick bites can cause allergy to meats.

An excellent review article by Moises Velasquez-Manoff (the author of the excellent book An Epidemic of Absence ) from the New York Times Magazine, 7.29.18  describes the evolution of our understanding of this newly recognized phenomenon.  

Meat allergy in this form was first described in 2009, and appears to be triggered by a tick bite. Initially, the tick identified was the Lone Star tick common to the Southeast. It is unusual in that most allergies are set off by an immune system reaction to proteins or lipopolysaccharides, but this one is triggered by a reaction to a complex sugar named galactose-alpha-1,3 galactose, shortened to alpha-gal, which is present in tick saliva.

To be clear, we are not talking about a tick-borne infection here, but rather to an allergic reaction to one of the contents of tick saliva. The reactions can be severe and life-threatening but often delayed (unlike anaphylactic reaction which can occur in minutes) by several hours after the meat has been ingested. Symptoms mainly consist of generalized hives and pruritis (itching) but at times can involve shortness of breath and swelling of the throat. The treatment is similar to that of other intense allergic reactions: injected epinephrine and/or Benadry.

Once sensitized, some individuals find they can no longer tolerate beef, pork, or lamb (even milk or butter). Cases of reaction to kangaroo steaks have been reported in Australia. It is not only the adult form of the tick which carries this risk, but the larval (seed) forms as well. It turns out that alcohol or exercise will exacerbate this reaction, and if the meat is grilled, it may be less reactive. It remains to be seen whether other ticks can contribute to this problem.

The moral of this story:  Check yourself for ticks after every hike; if a tick is removed early before actually biting and injecting saliva, this risk is clearly minimized.