Is this heat emaning from my charger normal at all?

[ohc1492]

I have a Flex2, charging it with the original quick charger included, but it gets incredible hot, like I-rather-don't-want-to-touch-it hot. Is this normal with quick chargers or is it my phone, or the brand?.. I'm from México, and on a regular household outlet. Haven't measure the time it requires to charge, but the heat is there before it gets the job done, not overcharging.