Some companies and or types of alcohol use differnet methods in distilling, maybe it might be something that is used to clean the bottle before distiller fills it / ingredient in particular brand or type of spirit that you are having a mild allergic reaction to, thus triggering the asthma / or possibly what the spirit is being mixed with eg post-mix cola, juice etc....

I found that when i was a bit younger that if i had a big night out on the drink and was drinking lots or mainly spirits that here in Australia come in a can or bottle that the pre-mix cola the company puts with the alcohol triggered my asthma.....i seem to be able to have a couple but if too many makes me sick.
My mother in law when she was younger discovered that she was allergic to he thing that they use to clean or sterilise wine bottles? Not quite sure what symptoms she has though