A growing red meat allergy spread by tick bites affects up to 450,000 Americans, CDC estimates.

A red meat allergy caused by tick bites, known as alpha-gal syndrome, is spreading across the U.S. and other continents. The allergy is triggered when a tick bite exposes a person to alpha-gal, a sugar molecule found in most mammals, causing an immune response that leads to reactions to red meat and other animal products. Initially linked to the lone star tick, the syndrome is now associated with multiple tick species. The CDC estimates that up to 450,000 Americans may have the condition. Managing the allergy involves avoiding triggers and tick bites.