Aside from the issue of tolerance, which can be very drastic, There are several medical issues that cause drowsiness, sluggishness, etc when exposed to certain alcohol such as allergies, diabetes, Celiac disease, etc. The list is quite long it depends entirely on the person and type of alcohol. There was a woman in college who had the smallest alcohol tolerance I’ve ever heard Seen. She blacked out on 2 beers.
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