In our 11 years of providing food allergy cards to travelers we have never had a customer mention this allergy. Just when you think you've heard it all - all languages, all destinations, all foods - along comes a new one: the official name is Galactose-alpha or Alpha Gal, for short. We had no idea what it was so as usual - we searched wikipedia. Long story short, it's a food allergy/reaction to eating meat (from mammals) and the initial cause of the condition is from a tick bite. So a specific kind of tick bites you, you suddenly develop a food allergy to meat and when you eat some, the hives and/or anaphylactic reaction is delayed by several hours. What a strange combination of events, food and timing.
Based on the fact that only one person asked about this allergy among tens of thousands of people who have contacted us, we're assuming the number of people with this condition is very low. But like I said , just when you think you know it all, you don't.