Virtually all keg beers produced by American and Canadian brewers are unpasteurized. That’s the whole point of getting it on tap instead of in the bottle (well, sometimes price is a consideration). It’s one of the things that makes tap beer taste different than bottled beer (of course you have to have a beer with actual taste in the first place to be able to distinguish).
Bottled beer will last a long, long time at room temperature because of being pasteurized. If you don’t keep your keg cold, though, it will spoil in pretty short order. Kegged beers imported from other than Canada will be pasteurized because it’s impractical to keep them properly refrigerated during the entire journey.
I always thought most (domestic) keg beers were cold filtered instead of pastuerized. This was a point made in advertising about 15-20 years ago when "genuine draft’ style canned/bottled beers came out.
A search of Google shows a few sites that claim keg beer is pasteurized, but a zillion claiming it’s not. I’m thinking it’s not (at least not the domestic stuff).
FWIW, the rule of thumb we used when I worked at Brewer’s Retail in Ontario (both in the retail stores and in the warehouses) was the following:
– Kegs were good for one month from the date they left the brewery.
– Bottles were good for three months from the date they left the brewery.
– Cans were good for four months from the date they left the brewery.
The above assume proper storage (a cool dark place for all containers, and in addition, refrigeration for kegs). Of course, if the brewer had put a “best before” date on the container, that took precedence, but otherwise, we’d count time from the date stated in the container’s date code. If a product went beyond the time limit of the rule of thumb, we returned it to the brewer. It was a point of pride in our stores that we only sold fresh beer–never out-of-date stuff.
We always kept kegs refrigerated, in the warehouse and in the stores, but we couldn’t be responsible if they were not kept refrigerated after delivery to the consumer (pub, restaurant, special event, etc.). Perhaps this is the problem the OP encounters: somewhere between the brewer and the OP, somebody has neglected to refrigerate the kegs he is drinking from, and the OP’s system is particularly susceptible to anything they may have developed as a result. Just a WAG, but maybe it’s the problem.
At least anecdotally among homebrewers, the consumption of some yeast slurry from the bottom of a bottle-carbonated (via yeast) beer can cause symptoms like the OP mentioned. Bottle-carbonated beers aren’t pasteurized since you need the yeast live in the bottle to produce the carbonation. You can tell one of these beers by holding the bottle up to the light and looking for a layer of sediment at the bottom.
It’s odd, though, that both he and his friend have those symptoms from kegged beer when presumably the average on-tap drinker at those bars doesn’t. Perhaps it’s just an unusual sensitivity.