What is the treatment for abscessed tooth?

Root canal / extract. Your dentist may first give you some antibiotics to get the infection down. Then, depending on the condition of the infected tooth, you may need a root canal and a crown on the tooth. If the tooth has a cavity that is too large or the tooth has a vertical fracture along the root or is splitting the tooth in half, then you may need to have the tooth extracted.
It depends. An abscessed tooth either needs root canal therapy or an extraction. This depends on a number of factors that should be evaluated by a dentist that can evaluate restorability and examine x-rays.

Related Questions

What are other treatments for tooth abscess and fistula besides extraction of the tooth?

Endo and Perio. Abscesses are always serious because the infection may spread to other parts of the body. Endodontic and periodontal treatments by a dentist is necessary to resolve the abscess. Good luck. Read more...
A few. Root canal therapy and/or periodontal treatment if the tooth is not already hopeless. Read more...

Isn't it unusual to to get very swollen when you have an abscessed tooth?

Yes. It is, if left untreated for a while. Most times the swelling remains minimal. Read more...
Quite common. The tooth may be the source of the infection, and that pus is just trying to leave your body. So inflammation sets in and it sometimes swells up just like a pimple. Please see your dentist, you don't want to mess around with this. Read more...