If you grapple enough and people fight for head control on you, it won't matter if you have headgear or not. It comes from constant friction caused by prolonged contact to the ear. The inside of the ear bruises and begins to fill up with liquid, causing deformation of the cartilage. It's very common in lots of grapplers (I've seen Judo and Ju-Jitsu guys with cauliflower ear). But I've also seen receptionists get it from prolonged used of phone handsets, which is the reason why they usually use headsets now.
It doesn't matter if you agree or disagree
... As long as I don't bore you and I spark a moment of thought, my goal is achieved
Queng leon queng tigre ecu tacacut, queca pa? - Pampangan Mandarigma Motto