The sugar molecule known as galactose-alpha-1,3-galactose, or "alpha-gal" for short, is found in mammalian meats and products -- but not in people. When a tick species such as the lone star tick bites a person, it can introduce the molecule directly into the bloodstream. The next time the bitten person consumes beef, pork, dairy or other mammalian meat products, the molecule can trigger histamines that lead to an allergic reaction.