Concrete:
Allergic reactions vary in intesity. I would expect both lips to swell, this is what we usually see. But we also see rashes, tongue swelling, wheezing and itchy or watery eyes. You have none of that either.
Other than an allergic reaction, I can't think of what else it might be. If it were something like a connective tissue disease (like lupus) it wouldn't go away so quickly -- nor would it be associated with beer drinking.
One could also surmise that eventually, both lips with be involved if you keep re-challenging your body with the allergen.
In any case, your query is noted and is a good legitimate question.
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