As a young lad I was not well off, I used to brew at home, formaldehyde is a by product of bad fermentation and a lot of beers "can" contain it.
Metabolisation of alcohol results in some aldehyde's being created in the bloodstream this is part of the hangover. That plus my home brew could often result is a serious headacheand I was a very careful brewer from the sterilization viewpoint.
My dad was a chemist (Pharmacist) he used to tell me lots of stuff like this although undoubtedly a lot of it will be out of date now or just badly remembered by me.
I think San Miguel Light (lager) is fairly clean you can drink ten of the things for 200 peso still be sober and still feel fine the next day, San Miguel from the dark bottles is foul though.
Red Horse at similar peso is another matter altogether
Jim