Use Cleanse.

Quit calling me a troll until you've tried it. How many of you actually know what Cleanse does in the first place? Have you even hovered over it? On a 210 second cooldown, you can clear ANYTHING but knockup and suppression. Anything. This includes Urgot's ult. Ignite. Exhaust. Every slow, every root, every stun, every taunt, all of it. Gone. Just like that. You get extra Tenacity for 3 seconds, too, making you that much harder to lock down.

"But Shingetsu, you idiot! ! It's got a much shorter cooldown and does the same thing, plus stats!"

It doesn't clear summoner spell debuffs. It also doesn't grant Tenacity. Great, you've clear Rammus' taunt. He immediately Q's and slows you, and his team jumps on you two seconds later. You're done. Additionally, you'd be shocked at how easy it is to get away from Ignites. Even in late teamfights, usually once someone puts out an Ignite while low, they focus on someone else and EVERYONE steers clear to avoid the KS. Early game, Ignite often leads to the opponent running away and /laughing while you burn to death.

If you Flash out in either of those cases, what do you accomplish? Nothing. They weren't chasing you to begin with, and you'll still die to Ignite unless you're really lucky or you ran Flash/Heal. But with Cleanse, no problem! You're just fine, even if you got Ignited at 70 HP.