Alpha-gal syndrome is an allergic reaction to most mammalian meats and animal products. In the United States the syndrome can be triggered by the bite of a lone star tick; other ticks can cause the syndrome elsewhere in the world. The tick’s saliva contains alpha-gal, a sugar molecule also found in the tissues of all non-primate mammals. In some humans the tick bite triggers the immune system to produce antibodies against the molecule, leading to allergic reactions when consuming meats and animal products that also contain alpha-gal.