What to do if your foundation oxidizes after application

Have you ever found your perfect foundation shade match only to find it changing color halfway through the day? After you’ve bought it full-sized? This has happened to me a couple of times already and here in the Philippines, beauty brands don’t really allow us to exchange them for a better shade. I’ve learned my lesson since so I’m extra careful with choosing my base products. Aside from swatching, sampling, and extensive research on reviews, it is also best to watch out for that dreaded color change brought about by oxidation.