Good morning Islay.........you sound on form this morning;-)
Yes, one can have skin tests to identify hypersensitivity(allergy) to penicillin but it is not always conclusive, but worth a go........even if the tests proved negative, my opinion in you case would still indicate an exaggerated reaction to penicillin which is not uncommon (about 10-15% of the population). Anaphylaxis which is the most dangerous and potentially fatal cause of death in an allergic response, is very rare.
You make a good point about the existence of a re structured stomach, but I can't bring myself to explain a connection.
I shouldn't get to worked up about last night's incident, frightening as it must have been and just note and monitor the situation.