Tooth abscess amoxicillin how long for swelling to go down?

Depends: Depends on the size of the swelling. If it is of an appreciable size, you may need to have an incision & drainage commonly known as an i & d. Regardless, once the swelling is of a manageable size, you need to have either a root canal treatment, or an extraction if the tooth is not savable. See your dentist or endodontist soon.

A few days: It take 2 days for a blood level. If it is not a chronic situation it should show signs of responding in a few days.

2-3 days: Typically antibiotics require 48-72hrs to become fully effective. If no changes occur after that period of time, call your dentist/endodontist, who will prescribe a different antibiotic. A root canal is needed regardless, as the cause of the abscess is coming from within the tooth, and the only way to treat it is via a root canal, or extraction.