I strongly suggest that you do a detailed allergy test.
With age, some allergies become more pronounced or revealed.
If it were only the first reaction, one could possibly argue that it was some tainted food. But the second reaction clearly demonstrates that you have some allergy that needs to be detected. Start from the list of ingredients given by CX. While you focus on the croissant (coz first incident) it could be some other part of the breakfast. it could even be psychosomatic because of your anxiousness over the first incident.
There are millions of CX croissants eaten every years without complains and the fact that you had twice a violent allergic reaction shows that you are the "cause" of the problem. And I get my sources from an allergy MD.