Several years ago, this newsletter discussed a new form of anaphylaxis due to tick bites. The syndrome is peculiar in several ways. Most importantly the anaphylaxis is delayed from the exposure by several hours. Also, it occurs after eating mammalian meat such as beef and pork.
Alpha-gal is a glycoprotein that is found in mammalian meats. The patient becomes sensitized to the alpha-gal from a tick bite because the ticks secrete alpha-gal in their saliva when they bite humans. In order to diagnose the condition, the patient needs to be tested for alpha-gal. They do not show a positive response to the standard allergy tests for beef, pork, etc.
The new twist is that certain round worms, such as Ascaris lumbricoides also contain alpha-gal and infestation with these worms can lead to the same syndrome.