[nicw]

It depends on the process. A more expensive spirit could use processes that uses less chemicals, but takes longer to filter.

Some wines are filtered using fining agents that contain gelatin, where some winemakers choose to use higher-micron (more expensive) filters. Or they use sanitation 'preservatives' like Velcorin. Any one of these processes could either trigger an allergy or add something that your body doesn't like processing.

The closest example is decaf coffee: how to strip out the caffeine. There is a chemical way (cheap but uses benzene) vs the swiss water process.

http://www.wisegeek.org/how-is-coffee-decaffeinated.htm

http://en.wikipedia.org/wiki/Decaffeination#Swiss_water_proc...