As per
FAQ:
I'd recommend checking out the
Fightworks Podcast interview with a doctor who also has experience in BJJ. On that same site, there was also
a post put up about the same topic. See also the article on
Grapplearts.
Cauliflower ear, to quote from Caleb's post, is caused "when the ear receives a blow that shears away the ear’s cartilage from its overlying perichondrium. Liquid fills the new space between the two layers, and will harden into a hard fibrous lump if not drained."
So in other words, any kind of heavy trauma to the ear can result in a cauliflower ear: that could be a small number of solid blows (again in that post, Robson Moura mentions that he got cauli after just one incident, so you could be unlucky), or it could be extended damage (such as driving the side of your head into someone else, as might occur when working for position in wrestling).
To prevent cauliflower ear, invest in protective equipment, like a headguard or earguards (since September 2008, I've used a
Brute Shockwave), commonly worn in wrestling. However, some people find them uncomfortable to wear, and in certain BJJ competitions (for example) you can't wear them.
To treat cauliflower ear, you need to get the fluid drained and then compress the area. It is important to go to a doctor as soon as possible if you can see your ear is flaring up, as without rapid treatment it can become permanent. It may help if you describe it in medically correct terms as an 'aural hematoma' in order to facilitate quicker treatment.
I've been training BJJ since November 2006 and haven't had any problems with cauliflower ear so far, but as the example of Robson Moura shows, it can happen quickly, so its worth being careful.