People usually didn't get sick from food before there was regulation and people still sometimes get sick despite it. What they really do is allow you to trust unfamiliar merchants whose reputation you can't know and so expand the reach of commercial society. But just as the rise of trucking meant that rail travel was no longer a natural monopoly and could set its own prices tools like Uber mean it's now safe to use reputational systems with drivers for hire. If there were some universal registry of restaurants that everybody checked for health ratings before going in to eat then maybe we could worry less about regulating restaurants too. But I don't see that happening soon.

An important difference between this and things like pollution is that in the case of pollution the negative effects of the seller's malfience don't fall upon the purchaser but upon third parties who don't have any say in the matter, what's called an externality. That's another case where we really do need regulation for a good result.