Alpha-gal allergy, illustration. Alpha-gal allergy, also known as meat allergy, is a reaction to the carbohydrate galactose-alpha-1,3-galactose (alpha-gal). Alpha-gal is present in all mammals apart from Old World monkeys and apes (including humans) and so is found in a number of meat products including pork and beef. Humans can become sensitised to alpha-gal after being bitten by a tick (far left) that transfers the carbohydrate (blue spheres) to the bloodstream, where the immune system attacks the foreign particle (second on left). When the individual next eats meat (second from right) the immune system mounts a reaction to the alpha-gal (far right) that can cause a range of symptoms than can include a runny nose, itching, shortness of breath, abdominal pain, or vomiting.