It certainly would.
Alcohol is a relaxant isn't it? So, is it actually relaxing perhaps the esophagus?
That still doesn't explain why the retching starts but it be like taking a medication to counter a symptom like how we can take Diazepam.
There are medications that do exactly that for people with physical illnesses.
You've seen people who have ruled out physical things, so have you seen a psychiatrist/psychologist? This is far too advanced for a GP and they might be able to work out whether it is a ritual of some kind or a medical use to counter an anxiety symptom. It just feels like you need an expert in that respect.
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Have you ever spent a week documenting this happening?
Aside from the event you would need to document things like thoughts at the time, feelings, bodily sensations (other than the retching one), throat sensation prior to retching, thoughts when thinking about using alcohol, thoughts after, sensations after. There would need to be things like environment, what were you doing at the time, etc.
I'm thinking a therapist might ask for something like this as they try to track down triggers. I have GAD & OCD so I had detail all my rituals when starting CBT and the usual way is to keep a diary for a week.
I couldn't do this as I had so many and they were short rituals, oftne back to back so filling in a diary would basically take up the rest of the day between the rituals so my therapist asked me to list them along with how many times, where I do them, etc.
There is an interesting case of retching on pages 384-385 of this book. Its also interesting how they treated it:
https://books.google.co.uk/books?id=...ritual&f=false