Yeah, you're fine. As you say, you will know if it's off. Manufacturers are very zealous with their use-by dates, most food last much longer. I've accidentally drank off milk before and, disgustingly, swallowed a bit. An upset stomach for 20 mins and everything was fine. No fret :)
The bacteria in the milk aren't pathogens, they don't want to infect a host, they just want to feed off the sugar in the milk, so they don't 'infect' you, but their presence in your body isn't pleasant.
· 3 months ago