Also, it's also important to take care of the inside of the body as well. Eat healthily, drink healthy. Avoid alcohol abuse and illegal drugs abuse. Alcohol could've also played a small contribution to EC. It's not good for the liver, gut, and internal organs.
Improper care for the internal parts of the body probably played a small contribution leading up to the EC as well. So, when one actually gets hit with a direct physical trauma to the lips, all of these small contributions leading up to EC didn't quite help when one gets a direct physical trauma to their lips.
For example, c.s. , you had someone bite your lip right before your lips got EC. That physical trauma was the last straw and sparked your EC in my personal opinion. That could have been a pinched nerve in your lip which caused serious trauma that had a strong effect/change on your lips.